Should I have two different commands for heeling? One command for head up focused heel and another command for casual sustained heeling/ informal loose leash walking? 

Yes, I have 2 commands. Heel for focus and walk for loose leash walking without focus.

I use my formal focused heel when my dog is doing competition-style heeling on my left and for my informal heel/walk, I have the dog on my right. (not necessary but creates more clarity for the dog)