Your boxwood is the same shape and density as the one below before I "edited" the branches. Nice trunk on this one BTW.
Mine was a mound of solid green with dense, DENSE interior branching. It took a while to actually "see" what needed to go and what needed to stay.
These boxwood will take heavy pruning. Leaving them "as is" will lead to long leggier branches with no interior leaves. That density will also begin to shade out branches and kill them off. I'd thin the interior crossing branches selectively, then trim back from the exterior on the rest, leaving some green on them. Backbudding is usually heavy after pruning old wood.
BTW, Wiring does very little good with this species, as branches "remember" when the wire is removed and usually go back to where they were when it's removed, unless you leave it on and let it scar the branch.