You can pretty much turn everything off and have an HST but I don't know why you would want to once you learn to use the features of the HST Plus. The HST is very good and many learn to operate one properly. Others never quite get over trying to drive it like an automatic transmission in their car or truck and it falls short of the tractor potential. The HST Plus closes that gap, but it is still a tractor with totally different operating requirements than a car, and the tractor will require different techniques than a "driver." The videos are an attempt to help some understand what their machine is capable of doing and how to convert that to work. Many lack the mechanical experience or aptitude to easily get there on their own.
Neither of the HST options are really difficult for most to master.
The "stall guard" you were noticing while bush hogging was the governor responding to load...and all tractors have them. It was able to overcome the load because you were running the right rpm and the right gear for the work being performed, which tells me you intuitively have some feel for proper equipment operation. Not everybody comes with that, and they spend a lot of time of these forums complaining about "poor design" and "unsafe..." when they are really the flawed design.
You will be fine with any of the transmission options. The HST options are just more functional for the tasks most landowners routinely perform.
Good luck.