No hard and fast rules from what I know, but I'm no expert. All I did was play around until I found what was comfy.

I ride +12 and -12 duck footed, stance width is wide...about 25 inches I think but couldn't tell you without measuring. Is just what suits me.

As for highback lean, the more you put on the more responsive your heel edge is to movement. For park I'd run it at no lean, and to be fair I do for all my riding but did used to play about and found I quite enjoyed 1 or 2 notches on the front binding when charging about. Also, at that time, made me bend my front knee more and get my weight over it better. But again, it's all down to personal preference