The performance of RO's strongly depend on the technology you'll use.

There are a bunch of papers available dealing with the sizing of RO's for optimal phase noise performance (or optimal tunability).
In general :
Start with a minimum-sized circuit, with as few delay stages as possible (3, 4 or 12 would be typical).
You can then do a simple parametric analysis for a comparison of the behaviour for sizing / power consumption / phase noise.
Gain and swing is typically of no issue (gain as high as possible for low phase noise, swing rail to rail - inverter).

Regards,

Stefan