Yes, seems that it requires longer clips from my brief testing. It probably has to do with tracking velocities and needing a certain amount of lead-in time for accurate prediction. That being said it seems like an abnormally long amount of padding.
Motion Bones are essentially which bones in the skeleton you want to be tracked/matched. Haven’t dug into 's system yet, but usually you can also weight the motion bones so certain bones matter more when matching motion.