The HPV cards are not accelerated for specific QuickDraw operations but are able to move data around quickly owing to the PDS design.

So the performance will depend on what you expect. If you are performing complex operations in Photoshop, the HPV will not speed them up. But you'll be able to scroll around the screen quickly and use overlapping windows. It just had to be good enough to work with the PowerMac analogue AV kit.