So you’ve got a pair of spacers and some shims to put the rotor back in the right place.
As above, it’s not going to fit an old Pro2 but will fit an Evo.
Yep, you’re going to be getting some additional space on either side of the wheel. The wheel may not end up central (doesn’t with the front conversion kit).
It’s a useful get out of jail, but given that you’re getting the boost sizing without any of the potential strength upside, I’d view any adaptor kit as a useful get-out-of-jail for swapping wheels around rather than a proper solution to a new frame and a wheel that doesn’t fit. By the time you’ve sold your old hub and not bought the adaptor it wouldn’t need to be a very expensive change.