I'm currently running snips on a RPi 2 (Model B) and it's working so far so good! Not too sure about the original Rpi though. I'm debating on getting a RPi 3 to see if the performance is better.
RPi3 is definitely faster. We also run on RPi 1/zero/etc.
What sort of CPU usage do you see? Picovoice claims 25% (on RPi3).