I had issues with Pop!OS as well, and after switching to Kubuntu, performance is much better.
It was likely due to the Gnome extensions I was using but without them, Pop!OS just felt really unfriendly to me. I like to be able to tweak everything, its one of the reasons why I switched to Linux in the first place and Pop!os just feels way too locked down compared to KDE. Like you mentioned, it kinda felt like I was fighting it at times, especially trying to change the file manager. What a fucking headache, never got that to work either.
Aside from that, Pop is a decent distro, and I think cosmic is going to make it a lot better because Gnome is really the biggest sore spot IMO.
Very true. I thought Pop!OS would be easier for me to use and get things to work and in some ways it was, steam didn’t give me grief like Fedora’s KDE spin did.