Welcome! I was actually in the same boat a year or two ago--every time I tried before that, there was a lot of finagling to get everything working. When I upgraded to Win11, and was having a rough time getting drivers going, I ended up trying Mint. Everything worked out of the box and I haven't looked back.

1. I find it helpful to have a separate data partition (though I don't actually use it for /home because I find that gets messy quickly). Separate data is nice in case you're concerned about something getting messed up, or if you like to try another distros (I ended up switching to Manjaro a while ago). Not necessary, but whatever you do, I recommend keeping it relatively simple.

2. Can't comment, haven't tried.

3. Last I checked, there was no client for Google Drive or Proton Drive. Not sure about Dropbox. I've heard of rclone but haven't tried it.

4. I usually try apt first, then check the GUI for a flatpak if needed. I personally prefer native apps/deb packages, but that's a subjective thing.

5. I use the default terminal and Firefox install. I ended up moving my actual personal data out of /home and it's been easier to keep it all tidy (there's even a way to point the file manager shortcuts to an alternate location). Tip: if you happen to have an Nvidia card, there's a GUI utility to switch to a non-free driver, which improved things for me. My other tip: especially if you have a separate data partition, give yourself permission to not get everything perfect, and that you might want a clean install somewhere down the road. Mint isn't quite as easy to reinstall as something like SilverBlue, but it's not that hard I've found.

Have fun!