I think you should try and find an instructor that drives the way you want to drive.
In my experience with SB, my first driving horse was one, The SB people drive in the ring only and do not take the time to really acclimate the horse to the cart and harness. They like them hot, you want, I think, a nice quiet safe donky for pleasure drives down the road and trails.
SB people use overchecks you will most likely not, they don't use breeching very often, you will, examples like that.
Try checking out eastern nebraska driving society on facebook, it is a closed group but they always want more drivers. Ask them to recomend someone in your area or maybe they are putting on some beginner clinics some time. If that doesn't work, PM me I have some other ideas.