On the suit front the thing I always bear in mind is that it is always easier to dress down than it is to dress up. Removing a tie or a jacket is much easier to do, and an easy way to start a discussion about company culture. Much better than belatedly realising the developers may wear jeans but this interview process also involves HR people or senior types. Unless the company is the sort of faddish place which makes it clear that they
never wear smart clothes I would personally always suit up.
"Business casual" especially is a social minefield. That said I don't mind wearing a suit to work, if you're vehemently pro-casual clothes then you might want to go the other way and make a point of it. That said I've yet to be convinced that in tech there is a time you won't need to dress smartly, even Zuck wore a suit recently...