Hi Tom. I always use Schluter Ditra crack mat and S1 adhesive. You don’t need S2 mate. I take it the screed is the fast track drying screed. So 14 days and you can heat/commission the screed.
Morning. As you say , remove existing floor covering and check what was used to adhere. Remove if required and prime. Slc the area. No need for anti crack if the floor is ok.
Ah right , that is correct on matting and loose lay system. Prime with an acrylic or sbr primer. 4:1 ratio. This helps adhesion. When levelled and dry , prime the slc as well. Helps the self adhesive matts stick better.