There are several different approaches to run flats. There is a goo that coats the inside of the tire that works similar to fix-a-flat that will fill the hole. Using this makes it almost impossible to balance a tire and you cannot use any of the shade tree balancing tricks (balancing sand, bbs, ball bearings, etc) because they will stick to the goo and make matters worse.
Then there is the rubber insert like this:
This device keeps the shape of the tire when it loses air and allows you to limp home. For this to work and not melt instantly or catch fire has to have a lubricant between the inner liner and the device. In terms of balancing using a run flat device like this in your tires creates more problems than it will likely solve. First is that it makes it impossible to air down your tires. As soon as you let a few psi out the tire then contacts the device and you lose any possible gains from running low psi. It will make it impossible to balance. This chunk of rubber is by no means a precision balanced accessory. Because of the lubricant, you can't use shade tree methods either. Products like centramatics might work, but not really a great solution. You typically just accept the fact that you will have a vibration if you are using them.