Installing packages from the AUR requires you to know what you’re doing. It’s not newbie friendly, even though AUR helpers like yay deceptively make it seem that way. Anyone can use yay it’s super easy and convenient (and you should use it, because of that) but if you are careless, it can potentially be unsafe.
That said, AUR is a fully transparent repository and if you know what to check, it is actually the safest way to install software, apart from the official repos, of course, which by using Arch or an Arch-based distro, you implicitly trust without reservation.
Here is some info about how to install software on EndeavourOS:
And about the safety of the AUR:
And how to build packages manually from the AUR:
Welcome to EndeavourOS! The best way to know whether this is the right operating system for you or not is to install it and try it out for a couple of weeks on real hardware. The only requirements are being literate (which you have demonstrated superbly with your endless walls of text) and willingness to use that skill to learn, by reading the manuals, the Arch wiki, this forum, and asking questions.
To make your transition smoother, consider sticking to the same DE you used on Mint. If not, Plasma is super easy to get used to, it has its quirks but it is the most popular DE for a reason (with Xorg, not Wayland).
All tadpoles are welcome, and some grow up to be majestic frogs.
The best way to know whether this is the right operating system for you or not is to install it and try it out for a couple of weeks on real hardware. The only requirements are being literate (which you have demonstrated superbly with your endless walls of text) and willingness to use that skill to learn, by reading the manuals, the Arch wiki, this forum, and asking questions.