Please keep in mind that when you choose a ship, max speed is only one criteria to look at. Sulha isn't the most recommended one in TA for nothing (cf. stats above). Max speed is the only measurable stat in-game so i wanted to check what the values were and especially the exact differences between ships since the bars aren't very precise.
All numbers are approximative (down to +/- 0-3 kph) and were gathered in the zero-g area of the P-AR219: Vishnu track.
Thanks to Interfector for Class I to Class III data.
From these data, we can find out that the AP (Augmented Propeller) powerup gives 8.5% more max speed for every ship at any class. The difference between a class I and IV ship stats-wise (at least for the max speed) is around 29%. Between a class II and IV one, it's around 15.4%, and between a class III and class IV, it's ~7.5%.
There's an anomaly in class I with the Buran having a max speed of 840 instead of the 864 kph expected. Reason (by dev. Korsaat84): "we really really wanted to stay away from the slightest hint of pay-to-win 😅".

The speeds are the same no matter the class. Credits: Interfector, Joltout.

• 28 kph: Asera, Buran, ESA, Lunare
  
• 27 kph: Sulha
  
• 26 kph: Koeniggswerth
  
• 25 kph: Conqueror

► Hold accelerate from the start, even during the countdown you gain energy.
► You want to start a time attack lap with the most amount of energy possible, meaning to prepare for a good lap, you'll need to eco near the end of the previous lap.
► Strafing doesn't make you lose speed. Reducing your steering by strafing more is very useful, cf. video on the right.

► A long boost is more beneficial than a short one, active powerup "turbo boost" is even better.
► A good wallbounce is when you're bouncing with the rear of your ship, or if proven impossible, with the side of it instead. That's also where drifting / counter-strafing can come in handy: You may want to strafe towards the wall you want to wallbounce while you still steer in the direction you want to go.
► AP, mS and OeT are the 3 most useful powerups in TA (Time Attack). I put them in usage order, AP is the one you'll use the most. Regarding when to use the others: "OeTs are usually tracks that have many smaller straights and mS ones are usually tracks that might have straights, but the sections with turns often have too many clustered together that taking mS nets a better time over all. Keep in mind as well, that this all varies with boost patterns" (Joltout)
► A specific sound (cf. video on the right) can be heard when a certain variation in velocity occurs: either a significant speed decrease and/or direction change.
► The general advice about wallbouncing vs oversteering is as follow: "what matters first is to increase the radius of your curve as much as possible and enter a corner without slowing down. Then, if steering and strafing at 100% still sends you to a wall, wallbouncing is the best option. Wallbouncing is also faster than oversteering typically when the latter shortens the ideal radius of your curve. If it doesn't, oversteering was the best option" (CredHC)

► "In class I Calima (Cairo) track you can work on the basis that your steering should be about as much as what's needed to do a 360° spin in 10s. Train for a 1st clean lap with Asera, this amount of steering and no strafe, no boost, no AP. Avoiding walls in this condition will force you to fix your steering timing and racing line. After that you can add constant strafing and decrease even more the steering while using boosts, AP, etc." (CredHC)

Here are 3 guides that could also help you, as well as a video from Majora:
https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=838061749
https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=1647276275
https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=964307276
S2riker also did a great playlist to help you improve called "Redout - Advanced Strategy Guide Series".
In Redout, you never release the accelerator. It can cause some strain, especially with the default control scheme on a controller, having to maintain the right trigger pushed.
Here's an AutoHotKey[www.autohotkey.com] script i did and use to always accelerate:
How to use: When the game displays "Press any key..." at the start of a race, press F9. In a tournament, you don't need to press F9 everytime, it will stay active for all the tournament. Only when you'll go back to a lobby or at the career event selection screen will it interrupt the fact W is virtually pressed down (that's due to the game itself).
F10 will stop the acceleration at any time you want. May be required to type in an online lobby.
Feel free to change the keys (F9/F10) if you want, and also the W in there by Z if you also have an AZERTY keyboard for instance.