You'll totally be fine. I've transplanted from miracle grow into happy frog with really no issues. You'll have to be aware of the slow release nutes that remain in the soil so you don't burn them, but that's not too difficult. As for disturbing the roots: if you're in flower, the less disturbing, the better, and if you're in veg, just don't butcher them. In fact, I usually slightly rough up the root ball when I transplant in veg, as I understand that it encourages new root growth. I try not to transplant in flower, though. Good luck and happy growing!
Cheers!