I'd like to contribute what I've tested and noticed.
Everything stock, including stock OC. No tune. All OEM fluids except coolant. I replaced the coolant with 90% distilled water and 10% (1 bottle) MoCool, so no BMW coolant. (I am aware and will be swapping this back out before winter; I'm more concerned about parts rusting due to water being used. Hope it's okay in the long run.)
Low rpm cruising in highway -> 95C (203F) steady @ 50-70F ambient
Give some gas and rev up in highway -> quickly drops to about 80-85C (176-185F) within about 5-10 seconds
Let it cruise again with low rev & throttle -> slowly ramps up to 95C (10-20 seconds) and remains steady
Low speed/traffic -> ramps up to 107C (225F) I've seen so far, but I have to be not moving for a long time (5min) to get there. Give it gas with air hitting radiator, it goes down quickly again.
At the track during ambient temps of up to 70F, due to constant high throttle input, I noticed the water temp remained around 85C (185F), and up to 90C (194F) if spirited tracking with more downshifts and higher revs. I did blast the heater one tick less than max, however from my observation, heater did not affect the water temp as much as it did with oil temp. Heater on = 240F oil, heater off = 250F oil, both at 70F ambient.
Hotter ambient temp tests to follow.