Power Maix M1w or Bit at 3.3v?

Is it possible to bypass the 5v to 3.3v regulator and power the M1w or the Bit directly from the 3.3v pin?

you can directly connect your 3.3V power source to module’s 5V pins, it will work.
only things changed is 3.3V pins are lower than 3.3V

Shouldn’t you be able to put 3.3V on 3.3V directly and ignore 5V?

You can’t do that. 3.3V is an output from internal EA3036 switching regulator which also generates the 1.8V an 0.9V needed for K210.
Applying only the external 3.3V is not enough, as other voltages are needed too. And in worst case scenario, you could even damage the regulator…