Max amount of 5V mosfets on PWM

I plan on using these.

And 10 was a ballpark. It says the aka gate voltage is compatible with any 3-5V controller. So which arduino and how many could it run? Also in the bildr guide connects the source to the gnd pin on the arduino. Could I ground to something else? I would think that grounding them all to the arduino gnd would be a bad idea.