Most "normal range" PZ screws are PZ2. Big ones say from No.10 (No.12?) and up are PZ3. PZ1 from No.4 down?
The fit of the bit into a PZ head is fairly positive provided the driver and head are not baddly worn. The point of the driver should fit flush with the head not disappear into it (PZ1 or 2 into PZ3) or sit proud (PZ3 into PZ2 or 2 into 1).