I bought a multi variety stone fruit tree (cherry, prune, apricot, peach) and tied each branch/variety onto wires in a fan shape to minimize the tree footprint. But as I read more on espaliered fruit trees, there seems to be differences between apple type trees that bear fruit along the main branch on spurs, and stone fruit trees which fruit at the tips. So I'm unsure now how to care/prune for the tree I'm trying to train such that it will successfully bear fruit. Should I cut each of the leader graft branches down a third (?) and then train one new shoot along the wire? Or another method? What's the best way to care for this tree? THanks]1
On short term, you should choose which variety you want to keep. Forget to have 4 varieties: they will fight to have food from root. Only one will survive. [Such plants are scams from cheap gardening centers].
Now you should prune continuously, to have all branches with the same strength. The top branches will get naturally more, so you should prune some more.
Avoid the vertical branch. Keep them as much as horizontal to have more fruits (and to control lengths).
You should check the buds, You will see two types (leaves and fruit), so you should not cut down too much or you will lose all fruits.
Prunes should be pruned a lot: they will not generate new buds on old branches, so it will become skinny quickly.
But you already have leaves, so I would keep them until you see flowers, and then you should reduce the branches.
Your tree is not so bad, so I would keep such long branches, but I would try to keep such form also in future.