More can always be said on the topic (personally, I think that the post-Napoleonic conflicts that aren't the ACW could use quite a bit more coverage on the sub); for the meantime, here's two particular answers that cover some of your questions:

• The sadly now-deleted u/elos_ has this quite comprehensive answer that sees to your first and last questions;
• u/vonstroheims_monocle takes on British uniform here. While the answer is rather older than I'm comfortable with, it is reasonably sourced.