I always thought Mint looked a bit ugly, but maybe it could be improved with some customization. It sounds like you might prefer something with KDE instead of Gnome. Both Pop!_OS and Mint are based on Ubuntu, so your experience might not differ significantly between the two. As another poster mentioned, Fedora could be a better option.

vars.yml is looking for a directory and file that don’t exist, and the readme doesn’t mention creating them. If you set postgres_password manually, it should work.

Welcome. Sounds like you’re going to be very happy here. Fedora is a great choice. I love what they’re doing with atomic desktops.