You can use the transfer button anytime. The generator is a matter of opinion. Personally I start it to cool the boat for cooking dinner and shut it off in the morning during the summer months. Winter I use it to charge batteries. If you run it while the boat is moving you have the possibility of the water intake coming out of the water in waves and pulling in air which will wear out the impeller. Depends on the boat and the intake location. I figure the less I run the generator the more likely it will work for the entire week at night when I am trying to sleep. Many charterers start it at the dock leaving and shut it off when they get back so I am in the minority. Personally I like the sea breeze during the day.
You can also run the engines with the right side pushed up more than the left to help balance fuel. The new Leopards now auto balance the tanks so the issue is gone.