GREAT THREAD ! My new to gravel experience (non racing) is limited to the wtb nano 40, clement mso 40, and clement ush 36. And is mostly on par with the above comments.
The ush is faster and just as cush as the mso 40, but a wider footprint is nicer in the loose stuff. And for very loose stuff, I'd probably rather have the nano's on. Not likely to try anything under 36. Looking for a 38 for my next pair.