Interoperability of hydraulic disc brakes and levers between model lines/manufacturers My bike came with  Shimano Deore XT M765 hydraulic disc brakes and Shimano Deore XT M756 hydraulic levers Dual Control units. 

I wonder whether the calipers from one manufacturer can be connected to the levers of another?

For example, can I connect 2018 Shimano XTR Race M9100 series calipers and rotors to Shimano XTR ST-M966/ BR-M965-F Hydraulic Disc Brake &amp; Dual Control shifters?

Alternatively, can I connect Hope Tech 3 V4 calipers and rotors to the Shimano XTR ST-M966/ BR-M965-F Hydraulic Disc Brake &amp; Dual Control shifter?

I want to mount this set-up on Fox Talas RL shocks.

What will be the issues of mounting these systems?

Thanks
You should have no issues with your proposed Shimano-Shimano setup. You may  confirm this using the Shimano technical documents si.shimano.com.