1. When making a dice roll as e.g. for deception, I would so much prefer to see the difficulty class of the check and my bonus to the roll. This will give me the feeling of my character's progression. If I just see how much I need to roll on the die, I don't feel if that's because the check is easy or I have a good bonus, and I lose that progression feeling (e.g. being rewarded for investing in Charisma). Also I won't get this satisfaction of succeeding at a high DC check, because I will never see that high DC number

. At least please add it as an option to see the DC and the bonus. This is also how all DnD players play it.
Additionally this will allow me to become aware of some conditional bonuses I am getting (e.g. +2 for interactions with some faction, although I am aware adv and disadv may be more popular)
2. The current huge upward jump mechanic really destroys immersion for me. It's not believable, considering it's not magic.
3. Please use present tense not past in the dialogue e.g. "I ask ...." and not "I asked... ". I play a lot of DnD (in California) and everyone here uses present tense. Or do just precisely what BG did, i.e. omit the "I ask" part. People loved that game, and dialogue format does not get old with new technology.
4. BG was famous for multiple and large responses that main character was able to give (e.g.
https://www.gamersdecide.com/sites/default/files/authors/u138905/dialogue.jpg ). I think this is really important part of the secret sauce of BG. Please do not make the responses the main character can have to be just small remarks nearly all the time. My character should be able to use full sentences, and sometimes even paragraphs. Also, as it was in BG, I think it was really important that what I see when I pick the response is exactly what the character says. (obviously, as in BG, there wouldn't be "cinematic" or voiceover of my character saying what I just read and picked, the action would move right away to response of whoever I interact with). I think this also adds more dynamism.
5. When e.g. guiding bolt damage is shown on the screen maybe instead of just showing number e.g. "13" you could show "4d6=13"? Of course I haven't playtested it, but I feel this may give me a better feeling I play tabletop game, and whether I rolled well or poorly. Maybe just allow it as an option?
6. I am afraid the bonus action allowing to perform a throw will be a chore, since I will e.g. feel compelled to always carry 10 pairs of heavy boots or something. Also when this extra action won't have a large impact on the combat, it will be not fun to use it, but when I will want to be optimal, I will feel like I have to. Even when that's not fun. A bonus hand crossbow shot (as with crossbow expert feat) does not feel as a chore since it has real impact on combat and scales with the character progression well.
I think bonus actions in current DnD 5ed are well balanced and you don't feel annoyed you have to use them or you would be handicapping yourself.
7. I feel that BG3 to too large extent becomes a combat tactics game. But I think that a very important part of BG 1 & 2 was world immersion, interactions with your party, and other characters, lore books (e.g. in Umar Hills in the inn you could find a lore book setting a stage for what later you may discover, and making it more scary), histories of some magic items.
8. A little connected with 7. Considering turn based combat, I hope it won't become a grind. In tabletop DnD nearly each fight is somehow important, and, e.g. as in Adventurer's League modules, you "solve a story" in 2-8 fights (with 6-8 being quite rare, and mostly applicable to 8 hour modules). (still there can be some exceptions, similar as Durlag's Tower was, but they should be exceptions). I really hope you will capture a good ratio between fights and story progression, so it won't feel like a grind. After all Baldur's Gate is supposed to be a role-playing game, not a combat tactics one.