The DSCS9 works best with Surface View off, and with H264 MP4 videos. Xibo does no processing of your videos at all.
I’d also say that the videos PowerPoint produces are OK, but they’re not super high quality in the first instance.
1080p should be fine, but its then down to the quality of the downscaling done by your TV if your sending a 1080p signal to it as to how good that will look at 720p.
You certainly could try setting stuff up at 720p instead and see if that’s better. The less scaling involved the better generally.