By far the most important thing I’ve done is created a list of all the package names. With just one command, I can reinstall all my apps.
The second most important thing I’ve done is created a long list of gsettings/dconf commands that configure Gnome to my liking.
I’ve also moved most of my user data off my OS drive to removable drives. But I don’t have my home on a separate drive since I don’t want to share that across different distros since they configure things differently. It’s also just a lot easier to not have a separate home.
Apart from that, the script I have also copies over some config files, sets my hostname, sets flatpak overrides.
I just listed the changes since GIMP 3 RC1.
Over GIMP 2.10.38, there’s a lot of changes. Better color management, GTK 3, non-destructive editing, and other stuff I can’t remember.
That last one is a major boon. It means you could perform an action on a layer, say raise the exposure, but revert it later on without affecting the quality or losing information. Unfortunately this doesn’t apply to all actions (such as resizing), but the list of non-destructive actions will grow later on.