I'm thinking Viburnum opulus. In either case if there are just a few places here and there where it sticks out too much just prune those parts back to side branches, leave the rest alone - what to do specifically, depends on what, exactly you are trying to accomplish.

Really embo? Those leaves look a little elongated to be opulus (10 foot sounds right though)- but I will definitely defer to your knowledge of shrubs. Still, as you say, it generally just needs the odd tidying up unless going for the full-on third of branches from the base sort of pruning in spring Unlike carlesii or bodnantense or even tinus, guelder rose can be left almost indefinitely without any pruning intervention from us.

If it has really outgrown it's space, you can coppice it on a 2/3 year schedule to control size and keep the natural form. If this doesn't apply, Tom gave you some good advice.

The leaves don't look quite like my maple-leaf viburnum which never gets taller than about 3 1/2'-4', so I think it's one of the other viburnums such as V. opulus as embothrium suggested.

Could be. Doesn't change maintenance regimen.

I've turned some of mine into multi-trunked small trees. You can try that if you like = you can just cut it down if you don't and it will grow back as a shrub form.