Coolant flow

Also, this bit about smog engines

"I know that most modern automobile engines run at well over 200 degrees, but that’s driven by emission regulations"

This isn't really completely accurate for truly modern engines. This is an opinion left over from when emissions standards got started, and it's actually backwards. The early smog engines, and we're talking 30 years ago now, started tuning for super hot exhaust temperatures to band-aid tailpipe emissions without really doing much else for the whole system. Heck most of those were still carbureted engines. And the exhaust temperature isn't controlled nearly as much by engine coolant temperature as the coolant temperature is effected by dramatically raising the exhaust temperatures. Look at some of the cooling systems on the F/M/J cars, they're not really any different at all than the A-bodies, but as you get into the late seventies there was air injection and all kinds of other stuff going on to raise exhaust temperatures. They had to tune the cars super lean, which raised temperatures, and inject air, which raised temperatures.

Modern engines with their all encompassing ECU's, fuel injection, variable timing, variable intakes, etc, etc, etc don't have to run a coolant temperature at 200° just to meet emissions standards. They're tuning more for efficiency, with also drives emissions. And if it was most efficient to run the engine at 160°, they would do it. And clearly you can still make a ton of horsepower and run at 200, it's not a mutually exclusive scenario.

That goes back to my original point- there are A LOT of ways to tune an engine, maximum horsepower is only one, and it's not best for every application. A Hellcat can punch out 807 hp and still run at 200°F, clearly there's more to the whole system than just emissions standards.