Don't go too low in your gearing. The Leopard is a fast tank. You want power and good low speed control, but you also want it to be able to rip around fast. The real ones can cruse at 45 mph.
I run my tanks in snow and mud. They do fine except when the tracks clog up with ice or mud. If it gets bad, it can stop the tank, and I have had ice and mud build up break track links and idler wheel mounts. I have never had an electronics issue with snow or mud.