I think 4k (3840x2160) 30FPS is the best video resolution to use, at least in North America. In Europe and other PAL countries you might be better off with 25FPS, not sure. With 4k, even if you're going to be displaying it at full HD, you can get better quality by downscaling the 4k video to full HD then by recording at full HD, plus if you want to get a high resolution photo out of it you can just grab an 8MP frame.
For slow-mo I think the setting is 1920x1080 120FPS.
To change the video resolutions just press the little gear next to to the resolution in the lower right hand corner of the screen on the transmitter.