There are several practicalities to respect in the power
train, and others at board / system level.
With discrete power FETs (10A or higher) switching losses
will eat you alive at more than a few hundred kHz using
power MOSFETs, worse with IGBTs. But low switching puts
you on a fat ol' ferrite and huge capacitors and makes
you have a slow loop.
Older bipolar PWMs can't switch past about 1MHz, themselves,
let alone smack a power FET around at that rate.
RF systems care a lot about exactly where the switching
note sits. Preferably right on top of some dirty-but-known
system clock, where you're already prepared to trap
and process out, or the umptyieth and umptyoneth odd
harmonic both sit comfortably out-of-band.