Depends on the scope being used. They are interchangeable due to each scope having a different length between the bells and knobs....will also depend on eye relief of each individual scope.
Yup.
Also, I might add, I want the rings as far apart as possible after getting the proper eye relief. So if the eye relief on the top scope is correct, that is the configuration I prefer. A wider stance means more stable under recoil and handling.