Yup, you’ll be fine. If a game has a Linux version though, you’ll still need to download some portion of it. By the way, just don’t use NTFS to play on Linux.
No problem! By the way, if Linux version of a game is broken (you’ll encounter those), or if you want to use Proton regardless, set a Proton version for that game before installing and you can restore your backup without downloading anything.