I do have some empirical data I can share.
The one place I had on my manifold for a temp sender, I used for the Megaquirt EFI. I drilled and tapped the boss at the BACK of the manifold for the gauge in the car. Using the computer to watch the real temp and seeing what the car's gauge read was enlightening. The engine quickly warms from cold to 185 and stays there unless it's real hot outside and/or I'm on it hard, then it'll climb to 190 or so. I have the EFI set up to turn on the fans at 195, and it cycles at that temp, and only when I'm sitting still. So I'm confident the engine doesn't get more than a few over 195 ever.
But the gauge in the car is a different animal. It's showing me the temp of the water that has passed through the block, (427 Windsor) but just entered the head where most of the heat is. When it's cold outside and I'm highway speed at low RPM I've seen it as cool as 120 degrees at that point, but when it's hot outside, idling it's showing 190-195.
So I would estimate when 50 degrees outside, at highway speeds, water coming out of the radiator is around 100 degrees, or a 90 degree drop.
When it's closer to 100 degrees outside, I'm only seeing a 15 to 20 degree drop. There's 2 reasons compounding to cause this huge disparity.
When It's cold, the radiator has a 140 degree temp differential to move the heat, so it's far more effective. Also, this makes the thermostat feather the flow way back through the radiator, so it has more time to lose heat. When the engine's inlet temp is 100 degrees, it can't take anywere near the flow rate to maintain 190 degrees out.
This is speculation, but I think a OEM pump at 6000 RPM will move more water that the electric can. I seem to remember it goes up to 5400 RPM, and has a smaller impeller. But The electric can run 5600 RPM when the engine is running 2500 RPM. Unless your at LeMans, I don't see anyone sustaining over 6000 RPM for any long duration.
Honestly, I don't think I would eliminate the T stat all together, but maybe put a 165 degree in with a 1/8 bleed hole to get to temp quicker and let the pump modulate from 185-190 degrees, then from 190-200 modulate the fan. Then you maye need some sort of PID control system with all of these interdependent loops and latencies to keep it from oscillating wildly. That's part of the reason I have the fan bang bang, on or off with a 5 degree hysteresis.
My 220 degree case was OEM mech pump, stock 195 degree Tstat, you're kicking it hard, then pull up to a light and idle for 2 minutes. At that point the metal in the head and block is 250 or so degrees, and the water comes almost to a stop with 800 RPM water pump impeller, and the water coming from the radiator is 175 degrees. For a minute or 2 the heat from the head and block will soak into the water quicker that it's getting changed. Let it idle another 2 minute, the fan will have the slow water in the radiator returning closer to 150 degrees, the engine is no longer producing much heat, and the heads and block cool down 10-20 degrees and all will settle back to a happy equilibrium.