I have found a way to make the "video window" stay the same size when changing videos, even works on repeat!
Turn on "Integrate Video in interface" and turn off "Resize interface to video size"...
...then turn on "Start in minimal mode" option, in the first tab in "preferences", which you can get to by;
Right clicking the video window, Tools | Preferences
...or Tools | Preferences from the main menu if visible.
Here are some keyboard shortcuts, because your controls will not be visible in "minimal mode":
https://www.shortcutworld.com/en/win/VL ... layer.html
Hope it helps for a few out there, tricky business!
Respect,
NiVofHiR