Fedora vs Debian Testing

Which one is good for daily use and gaming? And which one is up to date and has the latest kernel?

i’ll refer you to distrowatch.org which details the software versions for most distributions.

which distro is “best”, comes down mostly to personal taste and your personal use-cases.

what software will run on which distro is certainly a consideration, but unless it’s part of the repo, it often requires effort and a degree of trial and error.

by the sounds of it, you’ll want something well supported and commonly used - like ubuntu.