Percolation? Heat soak? Don't drive during summer??

Best operating temperature has a lot of factors. Piston-to-wall clearance being the big one. If it's designed to run at lower temps, then it will be fine. But typical clearances are designed for operating 190+
Oil choice also has to be proper in order to run lower (or higher) temps. Running 20w50 with a 160 stat is likely a bad choice - oil has to reach a certain temperature saturation point in order to activate the compounds which resist high loads, thinner oil gets there quicker.
Run 5w20 or 5w30 in the summer with a 160-170 stat and so long as the piston clearances aren't too tight, it should be fine.

Changing the operating temp after break-in could also be detrimental since the rings will be seated to the size of the bore at a certain temperature. Going from 195 to 180 isn't likely to cause a single issue. But drop from a 205 to a 160 and I bet oil consumption goes up a bit and blowby increases.

Higher operating temperatures are better for maximum energy extraction from the fuel - this matters for MPG. Best horsepower comes from coldest air charge, which comes with reduced operating temps (typically 160-170 is where max output tends to be found without other drawbacks).

Everything is a trade-off.