You can think that RHEL/CentOS is Fedora LTS
The option to upgrade once a year makes this more palatable, to be sure.
I haven't tried Silverblue yet, but that might make the upgrades faster and less painful.
That said I may switch to Silverblue anyway at some point, because it really is amazing in many ways.
I'm not surprised, but Flatpaks install everything in the user's home directory. So if you know you're going to be using Flatpak apps, make /home bigger.