At this point EndeavourOS Arm is a new adventure. So put on your Daniel Boone coon skin hat and play pioneer. Sorry I made it harder than it had to be.
The RPi4 with the 64 bit OS and anyone of the DEs is in my opinion a very acceptable desktop for most daily routines.
It’s obviously not for serious gaming, but there are some good retro gaming emulators available for Arm. An example, although not for RPi4, Ameridroid has a link to EMUELEC for a retro gaming emulator. The link goes to an ETAprime video review of EMUELEC for the Odroid on a Odroid C4. At this point, Archlinux arm does NOT YET support the Odroid C4, however the EMUELEC also runs on the Odroid N2+ which should run it even better than the C4.
Since uSD cards are fairly inexpensive, a SanDisk high speed UH1 32 GB uSD card is $9 USD at Wally World. So you can have one uSD for an EndeavourOS desktop. Power down, slide out one uSD and put in another, reboot and you now have a nice retro gaming emulator. Dual booting that is dead simple.
Anyway, have fun with your RPi4.