I would suggest you to ask on official Nobara discord. I got help right away.

Windows.

Never upload your passwords to any cloud. Always use good foss instead of proprietary software.

Use Aegis on android or 2FAS on iOS. And just backup your seed on hdd/usb stick. Dont upload on cloud.

For spider man recommended gpu is RX 580. I would suggest you, of course if you can afford, to go for RX 7700 xt or 7800 xt. You will be more future proof.

That all depends on what games you play. Do you want to play new AAA games or retro? Indie? What is your budget? XT is stronger version of regular 6600.

I don’t think there will be any issues. On that note, use open source AMD drivers. You dont need proprietary one from their site.

AMD all the way. Few weeks ago I finally made a switch from Nvida for the first time. I have no problems in gaming. All games that I play run same as on windows.