You might want to look at the vibration damping post for more info
There is much speculation about this, If you remove the power jumper JP1 then you dont need to remove/cut the power line fro your ESC. But this will the separate the voltage from the output rail from the rest of the APM, so you cant power APM via your ESC (you will need to use your power module) If you are not using the power module then its probably best to remove the red wire from all but 1 ESC (dont cut it but rather undo the clip so you can re-use the ESC)
Since the 880Kv motors and 12inch props are more powerful you might need to dial down some of the gains slightly, however in general it should be fine on defaults, start with defaults on your first flight and work from there 