Basically, auto choke position is the HIGHEST point towards FULL OPEN THROTTLE you can move the engine speed control (fastest setting).
To start a COLD engine that has auto choke, you will push the throttle control to the highest speed position.
Then you crank the engine. Once the engine has begun running you slowly back the throttle control down until the engine is running smoothly at the highest engine speed.
That point is your GOVERNED RPM point.
Backing down further will reduce your engine RPM.
Starting an auto choke engine that is already warm from use requires only that you move the throttle control to some point above low idle position, but below the governed RPM point.
Moving the throttle control all the way to choke to start a warmed engine can result in flooding the engine.
It is a good idea to put yourself a mark (Sharpie marker or paint pen) to note where the max gov RPM point is so you don't exceed that when restarting the engine warm.
That is not too big a deal to have to adjust to (so far as learning a new trick).
I hope that the carb controls on your replacement engine permit you to use the same throttle cable that came with the tractor (from OEM) and still have the fastest position and slowest position at the SAME end of scale .
I have swapped a couple of engines where the carb linkage was set up opposite of the OEM configuration which caused FAST and SLOW positions to be reversed on the throttle control scale.

Mownie . . . you are a very knowledgeable and articulate dude. Your reply was very exacting and focused. I now know what I got on the engine. Thank you.
If Briggs had technical support like you, they would be a better Company.

You are welcome.
I am just a dumazz mechanic that likes to talk :^)