The Epics frame rates all depend on resolution but, 5K 96, 4K 120, 3K 196 (i think) 2k 300
Scarlet frame rates, 5K 12, 4K 30, 3K 48 and 2K 60
So it just cuts it in half, so on the Epic in 4K your max frame rate in HDR mode would be 60
On the Scarlet your stuck to 15, at 4K momentarily, but they've said there is an update coming at some point which will enable HDR for 4K so maybe 48fps at 4K or some way the camera blends the streams in camera to only record one...not sure.
I use it for timelapses more frequently then anything.