I'm a novice to audio. When it comes to removing background noise should you do it first or last? Different YouTube videos recommend different things. If I remove background noise first it comes back after I amplify the signal and then I have to do it all over again. I feel like it's easier to remove background noise at the end but I feel like there's a reason not to do it? Maybe it works better with a softer signal than a compressed/hard limited/eq'd/normalized/amplified signal? Can someone provide me insight on what the best method is and also why?
I'd denoise before any other process.
If you compress anything before you denoise, then you're fighting against a moving noise floor, making the job harder. If it comes back after you start the rest of your process, it wasn't properly denoised in the first place.
If the noise was really bad I'd run denoise first as a separate process; otherwise I'd just put it first in the chain of processes & run it 'live' as I was editing. That way, if there were any sections that needed special attention I could just switch on the automation & 'edit around' them. That way if you move any parts, the automation will move with them.
Most of the rest of your list I'd consider part of the mastering, so would drop it into my final output bus, or a group bus if I was mastering over music/FX etc.
I tend to work in such a way that all my FX processing is done 'live' as I edit. I don't 'bake' anything into the file until the last moment, at export. That means I can always go back & change my mind. Hence also why I would only denoise separately before the edit if it needed particularly aggressive handling.
My workflow is usually Cubase/Nuendo, but similar rules should apply to most high-end DAWs.
on the off-chance you have to edit picture & audio together, if it was a particularly gnarly soundtrack, I'd edit in a video editor, then export the soundtrack & fix it properly in an audio editor, then re-merge. I don't like doing heavy audio work in video editors, they're a bit clumsy for my liking.