It might also depend on the OS version and hardware. 4K movies in my current cpu (core ultra 2 265K onboard video) on v4.2.4 are relatively smooth. But v4.3 is choppy. v4.3 also has problems rendering when zooming in non-video content like an appvm window. My prior cpu (i9-12900K), 4K video was choppy on v4.24.