Phil - yes, the drone is the same both ways.

Thanks for the chord explanations. The way PB used that sus4 was IMO purely to create tension, and I don't think he would normally have resolved it. On 'Streets of Derry' he ends each verse with a clash. Also, he would not have added a B to that GCD combo. I usually leave out the thirds when chording on a concertina, particularly on modal songs but in most folk stuff too, and that seems to have been PB's policy.