I have a Rise but I haven't really used the MPE features of Phobos with it yet.
I have gotten some info from Sandy at Spitfire.
I confess that I haven't had time to get back to it but I hope this will help others.
"Thanks for getting in touch. What follows is quite a long answer regarding MPE mode in Phobos, please let me know if you need any clarification on this.
When not in MPE Mode then Phobos will only respond on the specified MIDI channel. The main difference in MPE Mode is that it responds on any MIDI channel (the MIDI channel parameter is known as the MPE Master channel). An MPE capable controller, such as the Seaboard, will generally assign each note to a different MIDI channel (as much as it can). This allows pitch bend, pressure, etc to be be controlled per note (rather than to every note, as is the case with a normal controller).
With MPE Mode enabled, the modulation sources near the top of the list in the Modulation panels are all per-note (i.e., the sound will change according to CC, pitch, and pressure on the MIDI channel assigned specifically to that note). The modulation sources that start “Global..” (further down the list) are for responding to the master channel. On the Seaboard Rise, for example, the XY pad sends CC113 and CC114 on MIDI channel 1 (the master channel) and notes are allocated to channels 2 and upwards.
So in short, MPE mode changes the way that Phobos responds to multichannel MIDI, you can then assign mappings using the mapping editorfor the parameters that your controller outputs. If you are unsure what these are I would advise contacting the manufacturer ROLI as configuring their controllers seems to be quite an involved process and I would not want to give you incorrect info.
I just can't understand why the browser window can't stay open? Seems like such a little thing. Every time you search for a patch you have to click/ hold/ drag set. Ridiculous. Omni's Browser stays open and you can scroll and load presets with the arrow key on the computer keyboard. Is it really that much to ask in 2019?