the "Val" when type is Linear Regression is the "number=val*100" of values used to computed the Linear Regression, so yes val can be higher than 1.0.
With inertia, value must always been between 0 and 1
First explain me what you mean my more roll , say that don't make sens, except if you tell me the angle between what and what

So you mean roll angle between Head and track , or angle between Head and Cockpit !
The idea of the plugs always been to filter car vibration so the higher the value, the more the head will stay STEADY compare to the TRACK.
So the higher the value, the more close you will be to the Type = LockToWorldHorizon.
Please, try the LockToWorldHorizon, the LockToCockpit ... then val=0 with Inertia = LockToCockpit , and Val=1 with Inertia = LockToWorldHorizon , that's the best way to understand.
Now for the Min value, it's simple as that , taking roll as example, if Roll of car < Min, they Type = LockToWorldHorizon
Offset is just an offset, so if you put Pitch Offset = -10 for example, the view will be Pitched of -10° ( so head looking down of -10° )
About the delta plugin , I don't know, I'm just moving turning the head with the camera using Pitch and Roll value. nothing more.
Hope it help you understand

Cheers,
Seb