In general changing an esc shouldn't give you any extra top end performance unless you are hitting a thermal or current limit. In the Castle ESC you can increase sensorless motor timing to artificially increase the KV of the motor, but at a huge hit to motor efficiency, and we don't generally recommend anyone uses that setting.

MM2 vs MMP:
There shouldn't be any performance difference between the two. The MM2 will handle more power, but speed and acceleration should be the same between them. In sensorless mode they should run identically. They both use the same code base and there is very little difference in the motor drive algorithms between them. The biggest difference between them is the Monster has twice as many mosfets(36 vs 18) and is waterproof.