If I am not mistaking, the max/minimum speed is the function of the A/P and the warnings that it will generate.
The ESP is largely based on the settings in the configuration and it is meant to prevent unsafe maneuvers. If you bank past a certain angle that was set in the config, the ESP will gently push the stick to correct for over banking and the amount of force on the stick increases as that overbanking in degrees will increase.
If your pitch is too high that is getting close to stall, the stick will push forward to prevent that and if you are getting to a unusual attitude, the A/P will engage in a LVL flight mode. Of course all of these are accompanied by a warnings and to let you know that the A/P has been engaged.