I played with Endeavor years ago, but not extensively. If memory serves, it's pretty much just preconfigured Arch with some nice theming, a Calamares installer, and a few simple scripts. Garuda adds even more theming (too much for my tastes, actually), a few GUI utilities, notifications when your system is overdue for an update, and an update script that runs common post-update tasks (like grub-install) and takes snapper snapshots automatically, so basically user-friendly bloat.