Just finished my playthrough with the Shadow Ops classes, here's some detailed feedback on them.

tl;dr: Great experience, well thought out abilities and good internal balance overall. However a bit OP once you get the ball running.

For reference, here's the modlist i played with:
https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=807695319

Alright, here we go:

COMBAT ENGINEER
I used two builds for this class, the Smoker and the Shotgunner.
Squaddie: I'm a sucker for smoke grenades, so that S&M ability already hit a soft spot for me.
Corporal: Breach is fantastic. Since i played with Grenade falloff, Breach was often my only source to remove cover in the early game, but the ability stayed relevant up until Leviathan. I used Fastball on two soldiers and it was fine, but it's no Breach. I also tried Skirmisher, but i found it not impactful enough.
Sergeant: <3 Dense Smoke <3. Dense Smoke is the reason why i even beat the game. I used Fracture on a few shotgunners as well, and it was also decent, especially later when the boni to crits stack up. Slug Shot is poo, just like it is in the Perk Pack.
Lieutanant: In theory, i wanted to like Entrench, but i never ended up using it. Once i realised that, i just picked Focused Defense because its passive. I never took Moving Target, because i don't intentionally run Overwatches.
Captain: Pyromaniac and Aggression where my top picks here. While i see the use of HEAT, the actual ammo in the game makes it redundant.
Major: Combat Drugs for Smokers, Devil's Luck for Shotgunners. I guess i could've picked Resilience instead of Devil's Luck, but it probably doesn't matter too much.
Colonel: I like that Controlled Destruction is a thing, but in practice, i don't really end up needing to drop bombs on my own guys. CCS and Anatomist were both used about equally.
Brigadier: Devastation for Smokers, Slam Fire for Shotgunners. Because of Grenade Falloff, i was mostly using grenades for utility instead of damage, else Mayhem would've been a serious contender as well.

DRAGOON
With the Dragoon, i mostly settled into one build, a heavy supporter with WAR/Berserker suit. I realized the opportunity for a dedicated tank, but didn't feel like i need it.
Sq: Shield Protocol is a huge deal. Having a proactive ability that you have to use before being dealt damage, plays a lot cooler than the borderline lame Medical Protocol from vanilla.
Cpl: Tank all the way. I did use Lightfoot for the +3 movement on a few soldiers, but Tank seems like the better allround ability to me, especially since i use heavy armors on my Dragoons. I don't care about the Battlescanners.
Sgt: Whenever i took Dragoons with Stealth Protocol, i ended up running into some ♥♥♥♥♥♥♥♥ where i wished i had Renewal Protocol to deal with it. SP is really useful, but i gave it to too many soldiers, i guess. Advanced Shield Protocol didn't impress me much, i used it on one guy and never again.
Lt: Barrage is love, Barrage is life. Destroying cover and dealing damage to multiple enemies without caring about LoS is insane and i abused the hell out of it. I used Barrage like grenade spam is used in vanilla. I don't care about will or hack score, so this was a 100% no-brainer for me.
Cpt: I appreciated that having guys with the same ability here doesn't stack, forcing a bit of diversification among the troops. I think i ended up with 70% Shields up and 30% Sensor Overlays. I don't care about detection radius, so i never picked ECM.
Maj: Walk Fire has great utility, one of my favorite skills the Perk Pack got into XCOM2. I picked it most of the time. I put Aegis on a few soldiers and it was fine, too. Grace sounded redundant to me with all the Smoke, Flashbang and Poison that i already constantly used.
Col: Damage Control and Vanish are cute, but extra Shredstrom Cannons, Hellfire Projectors and Blaster Launchers win engagements before they even start.
Brig: I picked Puppet Protocol on my two guys, hoping to pick up something saucy in the last mission. Couldn't break through the hack defense of a Sectopod Prime and was sad :( I think i'd just pick Supercharge now, for an additional Shield and Renewal charge.

HUNTER
The Sniper rifle + Sword combo is probably my favorite and the Hunter didn't disappoint. On every mission, i took one Sniper and one Melee guy and they were brutal.
Sq: Fleche is so broken with Sprint :D
Cpl: First Strike for snipers, Snap Shot for melee guys. I tried Reposition, but all that happened was that i got annoyed because i had to end my turn manually...
Sgt: I find it hard to evaluate Point Blank. In the end, i didn't pick it with my main guys and didn't miss it, so i guess that worked out for me? Mark was nice, i like that it stays on forever and that it doesn't break concealment. Very useful and i used it on all snipers. Keen Edge was a no brainer for the melee soldiers and plenty powerful despite not really taking advantage of the shred (i had other sources for that).
Lt: I don't see a use case for Fade. Steady Weapon is a fine ability. But holy crap, Sprint is for Hunters what Barrage is for Dragoons! It lets snipers move and shoot and it lets melee guys run over half the map to Fleche a guy for 15+ damage. Woah.
Cpt: Bullseye does tons of damage AND applies a debuff? Sign me up. In theory, i alwys wanted a soldier or two with Tracking, but in practice i always ended up picking Bullseye again, both on long range and close range soldiers. As said before, i don't intentionally run Overwatches, so Lightning Reflexes is not something i care about.
Maj: With ABA2, enemies are pretty much always in high cover, making Precision insanely good. I did pick Damn Good Ground a few times and it was decent, but that +20 aim against most enemies was just too good. Low Profile is cool for melee users, but i often used Precision on those as well.
Col: Assassin for Snipers, Slice and Dice for melee. Evasive is too narrow for my tastes and the other two abilities seem much more useful in comparison.
Brig: Double Tap for Snipers (this was crucial on Leviathan, two of the Avatars fell to Double Taps), Butchers for melee. Last Stand is not an ability that i would ever use.

INFANTRY
Again, two general builds i used: The Rifleman uses the plasma rifle and pistol, the Bolter uses the Boltcaster and a medkit.
Sq: That extra ammo slot is genius and made this class really shine. I didn't use Suppression often, mostly as a way to 100% remove Overwatch.
Cpl: I like using Light Em Up with a Boltcaster. It allows me to shoot, then reload - while usually it would have to be the other way round. Half of my Infantrist got LeU for that reason. The other ones mostly got RfA, because it's damn powerful and synergizes with later perks. But i also experimented with Tactician and found it surprisingly great. It stacks with a Stock, dealing up to 6 damage on a miss. That's huge.
Sgt: Magnum for the rifleman, First Aid for the Bolter. Flashbanger is a nice ability, but not when stacked against two abilities like Magnum and First Aid.
Lt: Fortify on soldiers with RfA, Executioner on everyone else. Zero In is also okay, but i decided i would try and hit on the first try. When LeU is used without a Boltcaster, Zero In starts becoming more interesting, of course.
Cpt: Flush on everyone with Magnum. For everyone else, any of the three abilities saw use. Improved Suppression helps out with Codices and the like in theory... but due to my setup, soldiers without Magnum would usually carry a Boltcaster :) Therefore, i gave some of them Flush as well and others got Second Wind, an ability that i underestimated at first.
Maj: Good Eye is ... questionable at best. Resilience is too narrow. Focus is all around great. Easy pick.
Col: Coup for everyone with Magnum, Savior for everyone with First Aid. Elite for nobody, because those bonuses are completely irrelevant. I loved Coup de Grace, even though it feels a bit like cheating on my other love, Faceoff.
Brig: Full Auto is broken. There, i said it. It kills Sectopods, Hive Queens, Prime Sectopods and Avatars in one action. I also took Airstrike on some soldiers and it was glorious. I liked that one a lot. That giant hole i put into the Foundry facility when i finished off the Sectopod and his cronies there was immensely satisfying. Zone of Control i never got to test really, Full Auto and Airstrike seemed so much cooler than a souped up Kill Zone.

EQUIPMENT
Hollow-Point: Meh, they're free so why not.
Flechette: Never used them, didn't want to deal with an aim penalty on squaddies and Corporals. Later on, i had better stuff available.
Tiger Rounds: Shredding is hard to come by, these were much appreciated. I bought 2 and used them a lot.
Depleted Elerium: Holy crap, these are good. They are expensive, but sooo worth it. I bought 2 and had them in constant use by my Dragoons or Riflemen. My best rifleman actually got Shred from the AWC and together with his Elirium rounds, he shredded for 5 with each shot. That was nice in the endgame...
Reinforced Vest: Never got one, i had a short supply on cores and actually never went for a vest.
Smoke Grenade: 2 uses and they are free. I love this so much.
Flashbangs: They are free, but i am not quite sure why. I mean, i'll take em, but i would've gladly just bought two.
Nanofiber Vest: Never used it, seems irrelevant.
Plated Vest: Not worth the Trooper corpses in the beginning, too expensive later on. Not worth the equipment slot either.



All things being said, i had a blast. The beginning was really hard, mostly because i had to settle into the playstyle your mod dictates. But once i got the ball running, it was just fun. Some abilites in the later tiers are a bit broken and could use a soft tap with the nerf bat, but nothing tooooooo wild. Maybe make Full Auto have -15 aim instead of -20, but let the debuff stack up with each shot ;)