Adjusting the mini setup from default only gained me tenth or two per lap in the last season of the RDMC. Adjusting tire pressures often helped with long run consistency, but didn’t seem to affect anything too much. For me, that was the beauty of this championship, as I didn’t have time to muck around with multiple setup options like ARB, dampers etc.
Tyre pressure, brake pressure and wing level shouldn’t take too long to adjust to your preference, and I don’t think there’s anything else you can change on the Mini. For example, all I did last time out was keep wing at 1 or 2 and take a little pressure out the rear tyres, and nothing else.
I’m happy with fixed or free setup options, i don’t believe it makes a big difference.