Full weather compensation has no on/off. It is a constant demand, the only thing that changes is the target flow temperature, based on the heat curve, the outside temperature and the target indoor temperature. (Inactive setting)
(Active setting) Is similar, Constant demand with variable flow temperature based on Heat Curve, outdoor temperature, target indoor temperature AND actual indoor temperature. So its full weather compensation WITH indoor influence.
(Expanded) is the same as Active, except the room stat also acts as an on/off stat. You still have full Weather comp, the flow temperature will vary with indoor temperature also, but it will cut the demand for heat if the room exceeds the target temperature.
Theres not many systems where Id use INACTIVE, its more for 3rd party controlled zones.
I personally use ACTIVE, which means constant demand, but the lowest possible heat curve and therefor flow temperature are used, however you will need to set rooms to say 21 degrees, and keep tweaking the heat curve up or down till you have the system running steady maintaining and not overshooting a room temp around 21 degrees.
Most people will use EXPANDED as you dont need to be as accurate on the heat curve setting, as if its a little too high, the room temp begins to overshoot and the thermostat will cut the demand for heat until the room temp falls below target again.