currently I have moving/resizing on game capture disabled due to an internal misdesign, and the fact that games use multiple resolutions and can spontaneously change resolutions at random depending on user settings. I added the option to stretch to alleviate it for the time being.
However, when streaming a game, the best quality for the viewers will always come at a 1:1 pixel resolution.. well, or a 2:1 pixel resolution to compensate for data loss from YUV420. But anyway, for example, if you are streaming a 1280x720 game, you should set the base resolution to 1280x720 as well.. Or at least use the stretch option and upsize.