Push-pull configuration over single mosfet
If you don't mind that the resistive load receives a "power amplified" PWM signal then a single MOSFET being switched at the PWM frequency will be the most effective.

If you do mind (because you want a linear looking voltage proportional to duty cycle across the load) then a push-pull with inductor and capacitor filtering will be most efficient. Next most efficient would be a single MOSFET with back-emf capture diode but the diode would dissipate quite a few watts.

However, the single MOSFET solution is trickier to get right with respect to mark-space ratio. The push pull version produces an average output voltage which is duty * input voltage i.e. is largely load value dependent.

You could engineer a purely linear solution with one MOSFET but that would produce a lot of heat.