Depends, may be an element of suck it and see.

Real 2x10 cranks should have a different offset to 3x cranks but yours may not. I'm fitting a pair that seem to be from an S1000 crank to an old SLX M665 double and bash, but don't know how well this will work, yet...

I'm assuming you mean to make the triple crank into a double, btw. You won't be able to have a third functional ring due to the design of the outer ring from your double set.

The existing bolts from your triple won't work for the outer ring unless you add a bash or some washers as they'll be too long.

Are the chain rings the same bcd?

Any reason not to swap chainsets and run the 3x cranks with one ring (which you can ensure fits when you buy it)?

You can do but you'd have to use the 3x setting on the lh shifter instead of the 2x.

Are you going to be using the granny ring? As most 2x10 inner chainrings dont have ramps and pins for shifting up on to them.
if youre converting the 3x10 into a 2x10, as long as the bcd is the same and youve got the correct bolts 9x out of 10 you'll be fine. Just give it a go. Must be worth an hour or so of fettling.