Yes, all their images are purposefully normal fedora atomic images with stuff tacked on top. Some of that stuff comes in just scripts to make management a bit easier, some of it comes in the form of utilities like distrobox. They also come with zfs or proprietary Nvidia drivers or other things so you don’t have to manage them yourself, alongside tailscale and rpmfusion for nonfree stuff (like codecs). Some of them also have some light configurations, some of them have heavier configurations (especially in the case of bazzite).
You can totally do everything ublue does from a stock Fedora atomic image. Ublue just makes it a little more convenient. A sort of “oh, well I was going to do that anyway”.