Not really sure how archinstall factors in since it wasn't around yet when I first installed, but I love EndeavourOS. I've installed arch before, but I really can't be bothered if I'm just going to end up installing all of the same packages the GUI could give me in less time anyway. Yeah, EndeavourOS is just arch with some small extra packages and a GUI installer, but that's exactly why I like it.
Archinstall is not at all newbie friendly, especially compared to calamares and endeavourOS setup. Also, having a usblive is very convenient in case of problems.
If you don't have advanced knowledge nor want to customize it very thoroughly, I don't see any reason to use arch over endeavourOS. I mean, other than the fun of experimenting with the innards of linux, testing your frustration tolerance, and ending up being able to say "I use arch BTW".
Eh. Not quite. Yes, the main editions use Ubuntu as a starting point, but they remove a load of Canonical's cruft, like Snaps. They have their own suite of applications, the XApps, that are forks of other tools, as well as a number of other improvements and changes.
I couldn't say whether it's as far from Ubuntu as Ubuntu is from the original Debian, but it's some distance removed for sure.
And LMDE is based on Debian, skipping Ubuntu entirely.