The Back compatible version of PS4 has no problem and don’t need to convert any save files. It’s just games that have been upgraded to PS5. Still I have no issue too with No Man’s Sky. The PS4 save files just loaded on the PS5 version. Don't see any conversion.

Just use one account, set that account primary on PS5, then remoteplay with that account on PS4. I think you don't even need a psplus subs. Did this with my brother before I got myself a PS5. It streams smoothly 60fps 1080p with 40km distances.

Never used them, I just sleep to feed lol

Lol, I'm the other way around, love fallout 3 and 4, love oblivion but hate skyrim for its art directions