Trying to understand the impact of pruning...

Hello! I am new here and have 2 acres where I want to plant an orchard. I have read several books but am having trouble getting straightforward explanations/answers to a few specific questions. I  am trying to plan out how many of each tree I need based on microclimate, space, pollination, and water needs. I plan on running the space as a u-pick food forest type set up and plan on the trees, regardless of rootstock, to be about 7 ft tall. My question is do I base the spacing off of the rootstock or the standard spacing of the tree or the new hieght? I don't want my trees to be cramped or too far apart wasting space. If I am open to pruning is there any reason to get a dwarf rootstock? How would I estimate yield- is there a rule of thumb? I know if I take a 40' tree and keep it 7' tall it will produce substantially less but would it produce better or worse than a dwarf variety left unpruned or pruned at the same hieght all other things being equal?

When it comes to short trees you can do 4 things.
a) Prune a 30ft European cherry tree to 7ft
b) Graft a 30ft cherry tree to a dwarf rootstock
c) Grow Asian bush-cherry or Native North American sand-cherry or beach plum (only 7ft with no pruning)
d) Dont offer cherry, instead offer Raspberry or Jostaberry/etc

In terms of harvest/yield, One 20ft tree = Four 10ft trees.
20ft x 20ft = 400sqft
Four 10ft x 10ft = four 100sqft = 400sqft
So the yield per 400sqft or per 44,000sqft(acre) does not change. It just means that you will need 4x more trees and thus 4x more money upfront but at the end it is easier to harvest the plants.

As for spacing, it would be based off the new height
For your specific setup. I would put the rows 15ft apart to accommodate the walkway. And in the rows I would plant the trees 7ft apart.