Well, there must still be a reason that people are going to other distros… I don’t think Pop has any inherent problems (unlike Manjaro for example) so perhaps the average user (counting myself in there) simply considers those under-the-hood changes less appealing than new GUI stuff, especially when the demographic is gamers. Things like Cosmic’s improved tiling and the built-in theming support will be a major attraction, I think.
I have an X1 gen 9 and sleep-on-close worked just fine with Fedora for the time I used that distro (although it was KDE, not GNOME). Every other distro I tried worked as expected in that respect.
I use the free version for my Win10 VM. It works well, plus it’s super easy to share folders between guest and host. I’m not sure about 3D though, I use it for Photoshop & Illustrator.