you can also duplicate and then edit an existing profile, from thePhoton S profile you have to change the printable area and the printing time for each layer. that's all.
I just got my Mono X, and I can confirm that the printer doesn't recognize the .photon files generated by ChituBox, so you have to use their Photon Workshop for slicing. Chitubox can of course save out an STL of a complete part with supports, etc., for the other tool to slice, but of course it'd be convenient to avoid that step.