Hi

The Drive module is just an electronic feed-back to the main board of the drives turning speeds, in such a way that the Booster can auto-adjust the speed of each track, if you can adjust your drive speed via Tx, then this module is not a must.
You can keep your HL electronics, in fact, if you want, you only need the Booster (K=plastic or M=metal depending of your drive) to substantially improve the handling and manoeuvering capabilities of your HL tank. The tower/gun/sound/smoke can remain under HL control, TLS just improves all the stuff adding some functions like lights, etc.

The best way for you is to write to the ElMod guys telling them what is the configuration you have now, and the configuration and performances you want. They'll solve any doubt you have.

Regards