I am looking for a distro with a customisable UI. I want the ability to change everything in the UI: like changing the window borders style, animated interface, creating transition animations. Something that can allow me to create UI from my favourite video games. I am even willing to learn a language if needed. Just don't suggest arch because I'm only interested in visuals. I don't want to spend time creating and troubleshooting other aspects of os. Also, if above requirements can be achieved with changing the desktop environment, please suggest that too.
I am somewhat familiar with Linux as I used it a few years ago for some time. Back then, the games' support was lacking, so I switched back. But now with steam os and proton's contribution, games shouldn't be a hassle to run.
The truth is that none will allow you what you have in your mind exactly, unless you get down dirty and start programming it. However, some DEs are more customizable than others, e.g. KDE is more customizable than Gnome, for example.