Most florist mums are not garden hardy for sure. However, the disbudding technique works on both florist mums and hardy garden mums. I do have a florist mum in my garden that we received when my MIL passed away and it has lived four years without special treatment and is blooming now. Even in this zone though, most are not hardy.
There is no mum that produces huge flowers without disbudding. They are all naturally plants that bloom in sprays like floribunda roses. Some have bigger flowers than others.
Here is a disbudded down to single bloom per stem pot mum:
http://www.maygreenhouses.com/golden_gate.htmHere is one that has been pinched but not disbudded, not the same variety but showing the natural bloom:
http://www.maygreenhouses.com/yellow_elmira.htmFlorist mums are usually given growth regulators as well as being disbudded and tied. Otherwise even with pinching they grow too big and lanky. They use a lights and shade cloth system on them as well to make them bloom as they are plants that bloom on a short day length cycle just like poinsettias.
I loved all the fall mums when I was a florist. This one in particular:
http://www.maygreenhouses.com/rose_delano.htmand this one:
http://www.maygreenhouses.com/fall_delano.htmloh and this one:
http://www.maygreenhouses.com/pelee.htmlwhich was my most popular seller.
I really should go buy myself one......