In series or in parallel? Using PWM? If so what frequency? Higher speeds of PWM would
really need a MOSFET driver chip to get fast switching.
If you want to drive the MOSFET directly from an Arduino you _must_ get a logic-level FET.
What maximum current are you needing and what's the power supply(see my first question)? You need to calculate
the power dissipation in the FET using I-squared-R (ignore the nominal current rating of a MOSFET,
its only applicable if using extreme cooling measures).
Some of this has gone a bit over my head, this one of my first projects so apologies for my ignorance
The peltiers will be in Parallel, I don't know if I would be using PWM (should I use PWM?). Frequency wise I'm not sure.
Maximum current would be 28A, the power supply would be a max of 550W but in reality the power draw will be closer to 335W.