M111 is a good rootstock for many regions. You do not want rootstock that is too dwarf either. You'd rather have tree that is vigorous enough to cover the area than having a non-vigorous tree that fail to reach the coverage you want. Espalier pruning method will help to keep the tree size in check when using a more vigorous rootstock.

Fuji on M111 tends to take many years to fruit. Honeycrisp requires high chill hour to do well. If you have 800-1000hr of chill hours, that should be okay. Also, I have read that it does not like hot weather, especially during ripening time.

Google Espalier Apple Trees Rework and you'll get some useful info.

I have also read that not to do apple espalier on south facing wall because of excessive heat. Of course it depends on your location.

Multi grafted tree not custom to your situation is a bad idea. Usually the grafts are placed so you get branches in all different directions. For espalier, you only want them to grow in two opposite directions. You can buy one tree and do your own grafting as the tree grows. If I were you, I'd do some research to look for variety suited to your locale.

Google "apple variety suggestions for the southeast zone 7b/8a"

For espalier, especially one for a shape to suit your situation, it's better to start with a whip, with no branches, a bareroot tree planted in winter/ end of winter.

I recommend the book American Horticultural Society Pruning & Training to learn about pruning and training for espalier trees.

Duplicate post. This was discussed in some detail here