This is not entirely correct - the V1 to V16 are voices. You can tell the MIDI modules in your patch to be part of a voice, for example in the 4 voice preset you will see there are 4 MIDI modules assigned to V1 to V4.
When the SSP receives MIDI notes, it will assign the notes in a round-robin fashion to the voices. So the first note is handled by V1, the second note by V2, and so on. When you play a 3-note chord the notes could be handled by V1, V2 and V3.
So if the MIDI modules are assigned to V1 to V4 (like in the 4 voice preset) the first MIDI module will output the data of the first note, the second module the data of the second note, and so on.
You can configure the SSP in MPE or non-MPE mode in the global menu (third page, MPE toggle button).
MPE mode is used with controllers like the roli seaboard block, where the notes are assigned to seperate MIDI channels. If you use a normal MIDI controller you turn off the MPE mode. In that case, the SSP doesn’t care what channels your notes were sent on and assigns them the way I’ve described above.