For now, Smode promote seekable codec with frame rate restitution guarantees. (hap, prores...)
mp4 is badly seekable.
Full h264 support is pretty complicated, but if I remember well, I already successfully stream some h264 files in Smode encoded in .mov from After Affect. (may be by removing intra frames and letting all frames being keyframe in h264 encoder settings)
Hoping this can helps.