If you seal the tires up completely, I don't think the tires would perform well. When the tires try to expand, the vacuum would cause them to collapse on the sidewall I would think. I never tried it. You could try it and see how it goes, and if you don't like it vent the tires. If I were going...
The reason you vent the tires on bashers is so centrifugal force will expell any moisture you get in there. If your wheels are vented, moisture can get into the tire and mold will form in the foams. If you vent your tires, you can seal the wheels. Or just don't drive your RC in water and mud and...