I much prefer a more cinematic flow to combat and pop-ups that freeze combat is unimmersive and therefore eeevil. Yes, even in a turn-based game. I imagine something like a slow-motion effect when reactions are applicable affording the player a short time window to decide whether to react - similar to the renegade/paragon reaction check (but in slow-mo) of Mass Effect would make for much better gameplay.
EDIT: The current rigid pre-set system is unacceptable though. If Larian decides to go with this lazy implementation, they should compensate the character with more reactions/reaction resources as you can't decide to use as situations occur and therefore likely to waste many reactions stupidly.
I don't really know how, but I'm not sure it would be good to have reactions "like in Solasta" in BG3.
Full control over our reactions "like in DnD" is what I'd like. But probably not with a massive popup hiding the screen and pausing the game everytime.
Even if the Solasta system would be 200% better than the terrible toggle system we have in BG3, I think something more dynamic would be better.