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.
I think there is no out of the box such video players. Check plugins for mpv on screen controller, some of them may suit you. awesome mpv
Yep. IINA itself is just an alternate frontend for mpv.