The turntable stays in all the time, microwaving or using the convection. A convection oven is an electric oven with a fan. That's all. You can do everything in there you would do in a regular oven.
We have fulltimed for going on 14 years and that is all I have, no gas oven. I have loved it from the get go even though I didn't know anything about it when we started out. I also have one in our second motorhome and we built a Texas room in Texas and put one in there. They are easy, don't heat up your coach and can do anything you would do in a regular oven except maybe cook at 24 pound turkey. Just have to go smaller.
While the turntable stays in, the racks are used for only convection or perhaps combination cooking, not microwave.
Because air circulates during cooking, the convection cooks more evenly and sometimes a little quicker. I normally set mine for the minimum time when baking.
Dale