I regret I didn’t get to take a class on this. I would put it to use making a curing box for sausage and charcuterie. I know there are great instructions to be found on the internet for all these food control things, but I just haven’t taken the time to work with temperature probes yet. I have everything I need. I never even got around to installing the thermocouples in my pizza oven. Some day.
For most things, you don’t need an entire class.
Your thermostat works like a bang-bang controller, if it’s lower than minTemp, turn on. Higher than maxTemp, turn off. The output is either on or off. It works well enough for almost everybody. The thermostat I bought for the crock pot works this way.
The hot end uses PID, P just means, the further away from your set temp you want, the more energy you put into getting there. D means that as you are getting closer to your goal, use less energy to get there. And I says that if you are spending too long away from your goal, add a bit of energy.
P, PD, and PID controllers work for almost any control problem. Most of the other problems are because you have a very odd system. Then you need a class. You also need a class if you need to be sure that the control system is going to work before you start it.
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Or, from what I can tell, you want to numerically prove that your system is optimized. Empirical data can certainly get you to “good enough” (crock pots, reactor core coolant temps), but if you need to be sure you’re at “the very best” (space missions, smoker temp controllers), you need the proper mathy tools, and the thinkies to know how to apply them.
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Professors K and J have summarized an agonizing semester of my life.
Oddly enough we did a lot of reactor design, I still have some of them. We modeled all the equations but we ran variables brute force with a custom program to narrow down the ideals. It is so complex I was a little disappointed that this was the way we were taught to do it.
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The lab in our Control Systems class used national instruments DAQ controllers to try and control a mag-lev system. It was highly under-dampened and was not difficult to accidentally rail on one extent of the other. It was also fascinating in that you had to warn everyone in the class before starting it up to make sure everyone’s wallets were outside of a 10’ circle painted on the floor around the device as it had a habit of wiping credit card’s magnetic strips.
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By the way… did we ever decide which stepper motors and why for the OP?
Reminds me of a visit I made to Kirtland AFB in Albequerque. Was with a friend whose brother and sister-in-law both worked the high energy weapons lab. They had a 6 1/2’ tall magnet in one lab, and we were warned not to get too close for the same reason.
Ramblings
You think the laser questions you get here are tough? How about “How do I ensure that an array of mega-watt lasers remain not only focused on the same point thousands of miles away, but also remain in phase?” Yes, they worked on Star Wars… Each element looked more like a theatrical light than a weapon.
And the SHIVA star… 
Hundreds of mega-volt capacitors that could discharge in microseconds creating a collapsing magnetic field to fire wafer-like projectiles out of heavy stainless barrels; I want to say they probably had an OD of 4" and an ID of .75" at maximum. They started firing two projectiles at a time (symmetric field, fire one up, one down). But after there was an unplanned lesson in metal fatigue from the upward pointing barrel, and they found a 8" long chuck of it a quarter mile away (not to mention the hole in the hangar roof).
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I don’t make a kit for that very reason. I buy the MPCNC steppers in bulk to get a decent price on them. I am not able to buy smaller ones in bulk. The original build was meant to use your crappy (at the time) import and build a good printer out of it.
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Sorry, it was a dumb question. Hard enough to stock one motor, much less two. Anyway, bigger is always better…
Guilty as charged 
Exactly the information I’ve been googling for. Thanks!