mpv.net was designed to work and look like mpv but because of technical reasons there are limitations.
mpv.net implements an own main window and because of that all window related feature are not available unless mpv.net has an own implementation. Find mpv's window related features here:
mpv.net has currently implemented the following window related features:
autofit only single percent numbers are implemented like so: autofit = 70%
Some features have default values in mpv.net or are hard coded.
The input editor supports no characters that use 'alt gr', such characters require editing input.conf manually.
If you think that mpv.net misses important features consider making a feature request.