Encryption is enabled automatically in any version of multiplicity which supports it (all but very lowest end version I believe)
Due to the size of the data being sent by multiplicity there is no effective lag caused by it.
If you are experiencing any lag it will be either using wireless which is losing packets forcing resends, using software which 'optimises' your connection at a cost of large latency for small packets, or extremely high CPU usage or saturated network bandwidth.
Gaming mice with absurdly high polling rates will cause significantly more network traffic and CPU than normal mice.
