It's already not exactly 5e and a lot better. I think the only thing that has annoyed me (as a 5e player) is that jumping is something you can only do as a bonus action. In 5e, jumping is just movement. As in the "cost" to jump x feet is to use x feet of movement. There are still some restrictions about how far/high you can, of course. There were times in the game it would've been nice to jump twice in a turn but you can't.

Pretty much every other tweak is better. Especially the way paladin smite spells works (as in anything other than divine smite, like branding smite). The 5e versions of them are really terrible compared to divine smite. Divine smite you get to attack the opponent then once you know you've hit you get to decide if you want to smite (you even get to know if you crit). Other smites you cast before attacking and they apply to the next hit, use a bonus action, and require concentration. There are so many more resources involved and you could even lose concentration and lose it entirely. In BG3 the smite spells are applied to every attack for N turns. Might be a little overpowered for 5e, but it's nicer.

(Our DM has a house rule that all smite spells work like divine smite, it just makes it easier.)