The manuals, indeed are good, though for more esoteric issues I land too often on a gated answer page.
I don't care much about being fully RHEL compatible, or no ABI changes at all. I just want a system that gets security fixes quickly with as little chances of breaking things as possible.
Fedora CoreOS in particular has had a good track record delivering patches quickly. Like for CopyFail was pushed to the stable channel in about a day, IIRC, but the patch was already available within a few hours of disclosure in the "next" / testing channel.
Talos and Flatcar are also worth considering if you want an even smaller attack surface, from what I heard they weren't even affected by CopyFail.