So, my summarizing question really is - to drive general purpose N channel MOSFETs, do I need a 'standard' low side driver?
It really depends on the specific mosfet you are using, it's gate capacitance specifically and also the switching frequency you will be using and of course the actual drain voltage/current amount that will be switching. It's all related to how to eliminate switching delays for the mosfet to keep it's device heat dissipation as low as possible to prevent device damage. The AVR output pins are pretty robust and are active sinking and sourcing so many pwm switching applications using 'logic level' n-channel mosfets in a low side switching configuration don't require external driver help at all, just drive the gate directly with the arduino output pin. But again it's all about your specific device, applications, and how much load power you are trying to switch.
But to answer your question, if your using a n channel mosfet in a low side switching application then yes a standard low side driver would be the proper choice.
Lefty