To get same braking effect, the area of the pistons should br the same. Easy to figure out by measuring piston diameter as they are circular. I have magura marta that i coukd measure.
A differnce in piston size will give a different amount of lever travel and different amount of force on the lever. I have a deliberate mismatch using shimano xt lever for marta calliper, it works fine but slightly more travel than when using shimano calliper, i dont notice it when riding.