My two cents.
I think for the modern game a more extreme backhand grip is better (Gasquet, Almagro, Shapovalov). Can generate spin and handle the higher ball better. However, bigger grip change is a factor/need more time. So that is a consideration.
I'm also a fan of getting the strings facing up which is achieved by getting a lot of extension in the wrist (a more extreme grip promotes this) and getting the take back over the head./strings behind the crown of your head. note also the lifted left elbow. A huge drop, which straightens the arm will follow, and from there the arm can swing freely around as the shoulders open.
From here the racquet is going to drop a lot from the inside.
Tsitsipas doesn't really get the strings up at all. his wrist is more relaxed and his grip is more conservative than the above three. I'm not a big fan of this because I like the idea of removing variation; a more extreme grip promotes extension at all times in the wrist. Tsitsipas has a very natural and loose backhand, but he doesn't set up with a straight arm and he doesn't have full extension in the wrist and I think this is why he shanks quite a lot; those micro degrees his wrist can be offset kind of mess his timing, especially when rushed.
Fed has a conservative grip, but look how open he gets his strings/to the sky/behind his head. However you want to call it. Far more extension in the wrist. When you have a conservative grip and extend the wrist a lot so the face is open, it gives you the feeling of being able to "roll" over the ball a lot. Or shorten the swing and square the face for a return easily.
Now one backhand I am not a fan of is dimitrov, because his grip is so conservative he doesn't hit on contact anywhere close to extended. He is almost flexed, so he has to "roll" his hand an extreme amount to square or close the face. Talent can make it work of course.
Now if we think about which backhand has taken the principles of removing unnecessary movement better than anyone, the player that comes to mind is THIEM.
Conservative grip, straight arm with a lot of extension: Note also that Thiem chokes up on the grip, effectively making it a 26inch frame. Again, this is effective because it REMOVES degrees of freedom. He is gaining control with an extended wrist, straight arm, and choked up grip. This kind of promotes a longer take-back I guess but it's one of the reasons his backhand is such a weapon; he can swing out on that thing with a better feeling of control. He can rotate his body a huge amount, even more than stan perhaps, and because he opens the face WITH a conservative grip, this creates the conditions for that ability to inject huge flat pace at will.
Most one-handers are all very similar in technique--more so than another shots, because you cant vary teh grip that much or get away with a takeback that deviates from good form toooo much.