size and line thickness of zoom slider triangle

[peter51]

good day all.
i have a question regarding the zoom slider bar:
i noticed ,that in principle, there is a relation ship between size and line thickness of the zoom triangle and the video quality, eg uhd ,hd, sd.
but sometimes , even though its a uhd h.264 video the triangle is much smaller and the lines thicker than expected.
does anyone have an explanation for that performance difference?
also an other question regarding h.265 video.
with my new phone camera i made a h.265 video.
when i tried to play this clip in vlc, it ran for a few seconds but then became a stuttering sequence of frames. is that a vlc problem or is my computer just to slow.
and while i am at it: i use vsdc video editor for edits ( in uhd format) when the products (uhd format) are played on vlc, there are sometimes "smeared scenes" with a very nice , but not real colour display. the question again: is it vlc or my computer?
i dont think it is vsdc because the conversion has all the time in the world to produce the a good quality, new video file.
your advise or suggestions are greatly appreciated.
thanks for a great program
peter voussem
bne, au