What’s the line between “pressure” and “aftertouch?” – Roger Linn Design Forum

Maybe Roger covered this in one of his videos, or it is in another thread–if so please let me know if you know of a link. Here’s the thing. I have been using my new Linnstrument (128) with my Hydrasynth Desktop, modulating all kinds of stuff with “aftertouch.” On a typical synth keyboard with aftertouch, there is no “pressure” control, meaning, it is a gate on/off switch until you apply a lot of pressure, at which point it will engage the aftertouch control (this seems to be essentially what the pads on the HS desktop do and the keys on my Korg Kronos). I have never liked or much used aftertouch due to the amount of pressure required. On the Linnstrument, thankfully, there is a lot more control, where “pressure” exists long before you get to “aftertouch,’ (basically like a “z” axis, in addition to the x and y axis controls). I know this is basic stuff and you guys all know this. Here’s what I don’t understand, do MPE instruments (does the MPE protocol) have two separate settings, one for pressure and the other for Aftertouch? Also, I note that the Linnstrument has two separate settings (as far as I can tell), one for pressure sensitivity (low, med, high) and another button for turning “aftertouch” on or off. I don’t understand the difference I guess. Any help would be greatly appreciated.