I don’t think three in a hole is a good idea in the East. I know Dave Wilson recommends it but there in an area that has little Summer rainfall and low humidity.
As far as rootstocks if your wanting to stay at a six feet height I don’t think M111 is a good choice. The vigor is pretty high. G890 is also on the high vigor side but will work with some low vigor scion combinations. For example, I have Goldrush on G890 trained to a tall spindle system. I could keep it at six foot if I wanted to. But Goldrush doesn’t have high vigor and it is very, very precocious. I keep enough apples on the tree that it lowers the vigor.
I would take a look at this tree spacing calculator to get a better idea of how different variables interact when your planting trees.
http://fruitadvisor.info/tfruit/clements/appletreespacing.htm
Some of the new Geneva rootstocks are not covered in the calculator but you can use this chart to convert new sizes to old sizes. For example G890 is equivalent in size to M7.
Also if you’re just starting out I would look at this post (and the rest of the thread) it gives you an overview of picking the right trees.