This may be an unpopular opinion, but I think going with flatpaks is better for a beginner, especially if you’ll be using Arch. flatpaks ensure that none of your dependencies (these are the extra package the package you want needs) conflict with each other. Often these dependencies are very small in size, so your bandwidth shouldn’t take a huge hit. Unlikely to contribute to even 10s of extra GB a month. If you’re installing all of your packages out of the aur, you’re very likely to end up with hard-to-resolve conflicts or breaks on updates.
endeavourOS is almost ideal for a beginner who’s “into learning linux,” but there’s probably better options if you want a just-works GUI experience. I’d maybe recomend Fedora - their GUI is intuitive, they have all the systems management apps you want, and the dnf repositories stay more modern than Debian so you’re unlikely to ‘need’ a flatpak anyway.
Have fun on your journey and follow all the advice here!