I’ve got an RME Fireface 800. It is possible to setup a headphone mix in either application. I found it was a bit easier for me to use the control room functionality rather than TotalMix but YMMV.
I’ve since bought the personal mixers from Behringer (yes- I said Behringer!) and now use 14 outputs from the Fireface to a P16-I into the P16-Ms via sends within Cubase. It works great and lets the talent adjust their own mix to their liking.
Hope this helps,
-Rich