Arché is not supporting MPE functionality for the time being.
The instruments of the Arché Collection, just like a real violin, viola, and cello, are mainly monophonic instruments. On top of that, they feature a duophonic mode, that allows you to play so-called double-strokes on the instrument. You can however not modulate the timbre and pitch of the two notes in duophonic mode individually. They can only be affected together.