What should be the typical gain of an nmos only LC VCO? Should it be more than 100MHz/V or 200MHz/V or lesser than this? Which is more useful - keeping the gain high or low?
You can always change the gain of the PLL loop. What are you objectives?
Low gain means your VCO will be less responsive to random noise from your control loop; low gain also means you may have difficulty controlling the center frequency, if you only have 0v--2v from your PLL.