First of all you can check distrobox.it which can basically run Neon inside your distribution however you better set a different virtual home for neon in that case.
I would first tar the .steam to be on the safe side but steam is different, it is some kind of Ubuntu stable itself residing in that directory. Not a big time gamer but people laughed at Ubuntu for shipping its snap because of it.
Long story short I don’t think steam would have issues. I meant not to expect KDE guys to revert upgraded preferences back to KDE5 etc. You know they do such things and blame Linux/KDE etc.
It was a serious issue back then. People were wandering around on the Internet with root accounts. A lot of #linux IRC channels were kicking&banning anyone with “~root” or “root” ident with educational sentence like “Do not use root account as your ordinary account, check instructions”. We don’t see the issue widespread today since distros did very good intended “dark patterns” to push users to regular user accounts. Linux (or UNIX) “root” account is true god mode. E.g. infamous “rm” as root joke (!) could even affect Windows running WSL2, so MS had to implement special workarounds.