Haha, we have plenty of these narrow "badass drop" tracks
some years ago, I hated them, especially in spring time. Hard ice in the mornings, nasty mogul parcours in the afternoon. Nowadays I love to ride ("bomb") them.
Not sure what you mean with back-leg ruddering and dynamic turns.
I don't use my upper body for turn initiation on these tracks. Actually, with all the skiers on them, there's not enough space left to do proper turns. So I got it centered and stable and the legs do the work. Depends on how narrow I want to stay and how fast I want to be and how steep the track is. The steeper, the more work is done by the back leg, nose points down, weight on front leg, back leg makes the edge to edge transition. With this, you can stay very narrow and won't gain too much speed in steeps.
If there's slightly more space, I do rather fast edge to edge transitions with both legs equally engaged. Again, not real turns. Both legs bent low, weight slightly on front leg, the moment the edge grips put pressure on the edge so knees will stretch slightly and before the board really turns you use the momentum, change edge, force especially front part of edge and bend knees deep for next "turn". The faster, the lower and more weight on front leg. Dont "ask" the board to turn, force it on edge. Maybe that's not what you wanted to know/do, but that's how I do and it's fun