I tried on both the i5 and the i9 hardware and the results were not what I expected.
Actually H.264 video performed better and consumed less CPU than other formats, even in a 6 Fill channel + 1 Fill/Key channel (+1 iVGA channel for preview) configuration it was better suited for video loop playback (LED or LCD displays).
I stuck with H.264 at high bitrates and low keyframe interval.
Here it is working like a charm: