I would think that keeping the bow at a right angle to the strings would be important for a clean sound, whether classical or folk. I certainly find it helps-- (admittedly I'm neither a violinist nor a fiddler)--(play viola--mostly country or bluegrass viola these days.)

And I think the question of a shoulderpad has more to do with the person's collarbone than anything else. I need one--so I use a folded up cloth. It seems not everybody needs one.