I mostly install apps via Flatpak and Appimage (I use CLI AM appimage manager for that). I have 3 apps installed from AUR because it was the only way. I have a script and a cron job setup to run all updates bi-weekly at the specific time. I haven’t had any issues with system breakage in years. You don’t need to update your system this often, I just like to keep up. I wouldn’t go longer than 2 weeks without updating, the longer you wait, more updates, more chances of breakage. You can use any method you want to install apps. Flatpak is a container, meaning you can isolate (kind of) the app from the rest of your system. Benefit of Flatpaks, Appimages and Snaps is that you don’t have to worry about dependencies, everything is packaged in those apps. SO when you remove them, there is no chance you accidentally break otherr apps. To update the system use pacman -Syu each time you update the system. Use paru -Sua to update packages from AUR.