I completely see where you're coming from. Systems where Bards have actual songs that affect the creatures around them through their performance makes the class feel so much more like the magical musician they're meant to be.
BG3 is DnD5e and so the single-target flavourless bardic inspiration is what we'll have. If it helps I can at least assure you it's not a "nerf", it's relatively balanced within the system (although often awkward in tabletop as people forget to use it).
As it lasts all day before a rest, should I be pre-casting it rather than casting it in combat?
Does that even work?
No need to pre-cast, I think. It's an okay way to spend your bonus actions. It resets on short rests once you hit level 5, so you won't have to save it for later as much either.