MTB question regarding pedals and cleats and shims and shoes

Newbie looking at getting into MTB biking and doing a Xtera.

So, if I use Speedplay X2 on my road bike what is recommended for pedals with similar float for MTB?

Also, I have a shim on one shoe under cleat for leg length discrepancy. What is recommended for shimming MTB shoe?

Any recommendations for MTB shoes?

Thanks

How about the Speed play mountain bike pedals? Why wouldn’t you make the shim the same as your road shoes? What ever you decide on shoes-be sure they’re tri-mountain bike shoes.

I have size 12 Shimano MTN shoes I’ll let go cheap. Great for xterra because they are all straps. PM me if interested