Edit: I'm now enlightened and use mpv, I really like the ModernZ OSC (on-screen controls), and uses config files.
IINA is only on macOS. I looked up linux alternatives but none of them seem to have similar looking UIs, at least out of the box. I want the player UI to float on top of the video + with a blurred background, it as shown in the image; or at least the ability to theme it like so.
Yep. IINA itself is just an alternate frontend for mpv.