Looking at pricing the move to a 148 boost frame (JJ+) can I move my current gear over (XT 1×11 32x(11-46) I’m running square taper Middleburn cranks. Do these need to go for boost specific cranks?

Also do Shimano do XT or XTR hubs for 148 Boost?

The idea with boost was it kept the same qfactor (width of crank) and offset the chainring 3mm. You can probably achieve that by moving the ring from the middle to the outer position, many people say its not required anyway, youll find out once set up. Wider back ends can result in heel rub if you ride heels-in, so you might want a wider bb to resolve that if its an issue. Of course with taper BB you’ve got it easier than everyone else (as long as its not push fit 😆 )

You can, the ring clearance may be tight on the DS chainstay, it was on mine when I fitted non-boost cranks to a boosted frame.

As said above it’s ‘only’ 3mm offset

I put a non boost xt chainset with a 32t ring on my boost frame, chain line is spot on, never comes off the cassette, even when back peddling, only reason to put a boost chainset on is for better tyre clearance