I have an Aeromotive Phantom 340 system, which is basically their 340lph pump, return system - feeds rails then to regulator and the return, -6 (3/8) feed and return. No fuel heating issues or any issues of any kind. Pump is quiet as well. Easily feeds the 470hp engine.

The PWM is wholly unnecessary, its a "cost saving" idea at the OEMs. Even the corvette style one, you could change your fuel filter and the tolerance could jack with your fueling (bad parts out there).

You don't want to PWM just any fuel pump either.

So, In tank pump and return style is what I would recommend anytime.