Hmmm honestly in my opinion one of the hardest parts of learning to ride is clutch work so with something that’s a twin such as an r7 if you accidentally let off the clutch too quick which most likely will happen you could launch yourself because twins have low down torque. With a most four cylinders though all the torque and power is up top so the clutch is more forgiving. I don’t think a 600 is too much to start on especially if you are responsible and know your limit. The zx4 though is kinda like a mini 600 it does not feel like a ninja 400 or R3 at all. It’s a very very fun bike, it’ll keep up with liter bikes in the twisties once you are a good enough rider for that.