POP!_OS is very customizable as it is built off of GNOME 42 with system76's own COSMIC patches built into the desktop. You can use GNOME extensions like "Just Perfection" which will give you direct control over GNOME's desktop UI components.

I recommended POP!_OS because it's the most out-of-the-box GNU/Linux system. You can use POP!_OS as a daily driver and as a learning tool for Linux. I currently use POP!_OS right now on my laptop and gaming pc (with a proprietary nvidia card) after a year of not using it and I'm still kicking myself over glossing over it.