JonnyTeronni Hello. Just wanted to address your question regarding the difference between the two as I understand it.
Manjaro: A full-fledged distro that is Arch based, but increasingly using and depending on its own repositories and going in their own direction (for example, including Snaps ability by default as well). The Arch user repositories (AUR) aren't even turned on by default anymore in Manjaro (but most Manjaro users turn it on). It's rolling but tested for stability before pushing out to users. Comes with lots of installed apps and theming. So, in the end, it's starting to become more like Ubuntu, but Arch based and rolling. Has three core DE options (KDE, XFCE, and Gnome) and many community planned and maintained DE options based off Manjaro (excellent Deepin, Cinnamon, Budgie, i3, and others). Three distinguishing features of Manjaro is that they develop and maintain an excellent package manager GUI (Pamac), excellent GUI kernal installation software, and terrific GUI hardware/printer/driver detection and maintenance software.
Endeavour OS: By contrast, rather than a full-fledged distro, mostly going to be an easy installer for Arch and (eventually) many DE's (unlike Antergos, which was becoming more full-fledged, but collapsed under the weight of the work and volunteer efforts needed). Unlike Manjaro, theming will be light and installed software will be light. Unlike Manjaro, they'll have minimal to none of their own repositories (just what's needed for theming and installation software) and will depend exclusive on the AUR for software (which, again, Manjaro now turns off by default).
Also, between these two in features and build-out, also Arch based, is Reborn OS, which is collaborating on developing the installer software with Endeavour OS.
Hope that helps.!