The resistors are there to help reduce electromagnetic interference (If I remember correctly) generated by the motor.
As far as I know, keeping them on will have a very minimal effect on their performance.
Cutting them off wont effect the motors either but might mean you have receiver problems. But if you are already running 2 motors without EM suppression then its unlikely to matter.

And part of me thinks that they are not resistors but something else? I cant remember...

Hopefully this is of some use...