Currently waiting for the Rohloff rear wheel for my wife's touring bike. Currently it is set up with a Shimano Deore triple Hollow Tech II. I could probably use this crank with only 1 ring. But I would like to explore what some of you might suggest. Would like to stay with the Hollow Tech II so the BB are the same om both of our bikes.
I see that a number of cranksets are 1x11. Is there a difference with these is using a single at the rear?
Thanks!

The chain line might be off with the Rohloff, depending on which position on the triple crank you use. Those 1x10 and 1x11 drivetrains are set up with the chain line straight for the rear cog that is expected to be used the most. Anything above or below that cog will be off a little. With the Rohloff, you'll want to get it as straight as possible.

What advantage is there to having the same bottom bracket on both bikes?

If you get a square taper crank, you'll be able to choose from a variety of bottom bracket spindle lengths to set the chain line right. This is much harder with a Hollow Tech.