I've got these brakes in 2 setups currently:
Onirii m4 - full original setup.
Onirii m4/PRO E4 calipers with Shimano bl-m6100 levers.
Running the same sintered pads in both, and same disc sizes.
Parts off Ali $70 a set n $25 per caliper. (Lookout for the deals!)
Power wise even the stock onirii's are good.
BUT once you add the Shimano servo wave they are up another level!
The stock levers have a bit of flex when really pulling hard, and the piston size means the top power is not as good as it could be.
Cue Shimano levers.... They have zero flex even when pulling hard, and smaller piston means higher top power.
But the servowave means that the lever pull isn't too far.
Result.... A much sharper feeling brake, with better power.
I do also still feel that the caliper has a bit of flex under extreme braking.
All in all, good brake on its a own, great brake with Shimano levers.
Scar