I'm reading about 20s vs 22s and I think the general consensus is that 22s offer a firm ride, look silly when suspension in Normal Mode but look nice when lowered and 20s offer a more comfortable ride but may look too small for the vehicle (shoot me down if my research is incorrect!)

Why then is there a lack of people opting for 21s or little info mentioned?

I've not even purchased my RRS yet and love the look of 22s but am put off my the harsh ride quality and look or the RRS in Normal Mode.

This one looks spot on for me but not sure it could be driven at this height!

You can drive the RRS at a lower ride height but you have to do a bit of work to do so. If you want 22in wheels and a low stance in order to get a certain look then you need to either invest in an electronic tool (EAS Tool, IIDTool etc.) or some lowering links. Then you can have the low look all the time. 2012 SDV6 - it's missing a couple of cylinders
2008 TDV8 - it was a labour of love and is much missed

Those wheels look great  LCFC. Receiver of threatening letters from Overfinch.