I like hydraulic brakes a lot, but mechanical vs hydraulic is just a different kind of transmission, power is still all about leverage, and they have about the same amount.

Try to really dial in the gap. Hydraulic brakes are self-adjusting, mechanical calipers you can dial out the slop by screwing in the adjusters by either pad until it's just barely not rubbing, and take up cable slack with the barrel adjuster. If you use up all of that slack then you can undo the pinch bolt and pull some more cable through. If it still has a big gap when it's nearly rubbing you can probably see that the rotor is warped and you can replace it or try to bend it back.

You could also look up pads for your caliper and whichever material you have, try the other one (sintered metal vs organic/resin/semi-metallic)