Current starving may degrade gain while it degrades
(on purpose) drive. At low operating frequencies you
might prefer to have a composite inverter with high
gain and only a variable output current (say, starve
only the third inverter of a trio chain, each trio being
one "inverter". Or you might prefer unstarved inverter
and a RC lag network with the capacitor being a MOS
varactor. Switches have minimum MOS noise, resistors
are as good as it gets, and the cap bias you can filter
the heck out of. But current mirror MOS are pretty bad
noise actors and in a simple ring design they are direct
to the output.