I love EndeavourOS but I wouldn’t say it’s a lot easier to use after installation. Sure, the installer has GUI, but after that, you pretty much have a vanilla Arch with a barebones startup guide. When learning to use Arch, I honestly spent the same amount of time on Arch wiki, regardless if I was using pure Arch or Endeavour.
Nevertheless, EndeavourOS is a great distro and I recommend it to everyone. Just remember that it’s Arch with a GUI installer and some tips at the first startup.
Depends on how you used Manjaro before, since it’s made to be user friendly, has GUI for pretty much everything, out-of-the-box optimisations for gaming, etc. If you used all of those functions and not much else, I’d say there is quite a bit of a learning curve. However, if you used Manjaro as a power user and tinkered with lots of under-the-hood options, then there’s not much difference between Arch and Manjaro, except that installation and initial setup may take more time.