What’s the difference between setting up a cue mix in the control room routed to the headphones out and the Headphone mix?
don’t they both just do the same thing?
I mean if I want 4 cue mixes then I set up the 4 cues in the control room and route them to the headphones.
why is there a separate ‘headphone’ mix type in the control room?
MC
Because the headphone is for the engineer in the control room, and provides extended options, like for example listening to all the different cue mixes, and then some…
But I can listen to all the cue mixes on my headphones anyway without setting up a headphone, just from the control room. If I cycle through the various cue mixes using the tabs in the main control room mixer I hear on my phones exactly that, hence my question 
MC
If your hardware has this function, then you don’t need to set one up in the Control room, You’d only need this if your HW didn’t have the facility.
E.g. I have a UR28M which has 2 Phones out. The Phones 1 is hardwaired to the mix 1 bus the phones 2 out can be switched between any of the mixes - so I make my mix 1 my cue (artist) mix (I only need the 1 in my case) mix 2 is then my main, and mix 3 can be a FX or send or whatever. Phones 2 is then the obvious choice for the engoineeers phones in this case. In the Control room I don’t set up a headphone channel at all. Similarly the 2TR input can double for me as a talkback should I require it so this too is not set up in the CR. The UR28m also features mono, dimming and muting so I don’t need these in the CR either even though they are at hand.
Basically the CR offers all the facilities you might require, but you don’t have to use them if you don’t need them.