PWM is step down, it's what Provari uses for step down, it's what Vamo uses for step down....
If I build a 1.6Ω single coil on a simple IGO-W and put it on my mech mod with a fresh battery, it's 11 watts (4.2 volts), pure DC voltage, low voltage drop, a laboratory standard 11 watts.
And it vapes differently from my iStick at 11 watts, I know that going in....
It vapes differently from my MVP-2 at 11 watts, PWM filtered to a flat DC voltage
It vapes differently from my VTR at 11 watts PWM
It vapes differently from my Spire at 11 watts in RMS mode
It vapes differently from my Spire at 11 watts in AVG mode
It vapes differently from my VV Gripper at 4.2 volts (it's only VV)
It vapes differently from my semi mech mods, as there's additional voltage drop.
And none of them vape the same as any of the others in direct comparisons at the same settings with the same topper. Switch to different toppers and some dual coil toppers and the differences are even bigger. And as the battery charge drops different mods do better or worse in keeping the same vape level.