Something not right. If you’re doing a workout (in ERG mode) then you stay in one gear and the trainer will alter resistance to give you the specified power target.
There is no drafting in group workouts. The speed of the rear wheel on a smart trainer on Zwift is irrelevant.
Assuming you have ERG mode selected in the settings then you need to zero offset your Stages PM. Zwift then power matches it to the Snap.
The 100% difficulty setting is for riding Zwift in Sim mode. Has no effect in workout mode. Google it to get an explanation. I have mine set to 40%.
well if it “group ride” workout, you all go the same speed ( that is new thing) and on the ERG mode it lock you in at Watts if you spin at 100rpm or 50rpm you still being doing 200watts, it just hold you to it.