Visually marking out the 5ft square

Here's another one, this time talking about attacks of opportunity

On the subject of "if you start the fight you should get first hit" well... not really.
If you have a nice DM, they might let specifically that character throwing the first punch to act first without initiative, then ask for initiative rolls. If you have a really nice DM, they will give each party member one action outside initiative before asking for initiative rolls. The AI that counts as BG3's DM fluctuates between borderline nice, and a sweaty rules lawyer who makes shit up for themselves, but never lets their players get away with anything.