Having factions be "expeditions" or with their LL being "on vacation" is not ideal. TOW still has plenty of them, but I dislike them.
Putting two LLs in the same province is a no-no. And ideally they wouldn't be in adjacent ones either.
Having a part of the map with no LL at all is not ideal. Some parts are "meant" for modded factions (TEB, Araby) but I'd also like the space to be utilized even if you're playing without them.
CA placing a LL somewhere, even if it's kinda dumb, is a decent reason to just follow along and do the same thing. Don't forget these WHTW games are (some type of) canon.
If you're trying to find a spot for a LL, don't just think of that LL, keep the existing/surrounding ones in mind too.
Try to consider and preserve the game mechanics of each faction. Sometimes they are map-specific, but see if you can find a way to make something equivalent.

Lizardmen, Dark Elves, High Elves, and Cathay, it is just not their campaign.

(Kroq-Gar made the most sense to put in Konquata by default. Mazdamundi is a very close second.)
Anywhere where it would make sense for them to be would a terrible starting location.
For the Dragon Isles and Sotek's Trail (south east jungle), both between a rock and a hard place. Either you expand into Nurgle's Realm, or go the other way and immediately walk into another legendary lord (Khalida/Helman). I don't like it, feels too restrictive and crowded. Easy solution, put Oxyotl there!
Estragan's Island does make some sense, since there is supposedly a lizardman temple on it. But because of it's location, it'd have to be framed as if the lord was attacking Galleon's Graveyard. Can't think of a motivation for that, even Sigvald has something lol. Also would need to find a new spot for _____, a minor thing, but another complication.

It just doesn't make sense to put them anywhere in the Old World proper. Can only put one guy at Nagronath/Albion and I picked Hellebron for some reason. Maybe Morathi would've been better, but there's always hope I go insane and put her in Slaanesh's realm or something.
There's that sunken Black Arc settlement in Galleon's Graveyard. But then we're back to inventing reasons why Malekith is trying to take it over (also _____ needs to be relocated in this scenario too).

I dunno, for both, they're rulers and tied too heavily to Ulthuan. If they're going to leave, it'd be for war against their enemies, and since Dark Elves don't fit too well into the Old World, they don't either.
Elftown makes some sense, but it would be such a bad start. Okay maybe not bad, but very unusual, too unusual to be enabled by default. With MCT you can see for yourself.

Or Zhao. It's one of those annoying expeditions either way.
"Path to the East" doesn't work anymore because I put Thorek there at Karak Vrag,
For "Spice Route" it's maybe too crowded with Ghorst again. And I think even the Burning Wind Nomads being there doesn't make too much sense, since that road only goes to Cathay indirectly.