Most have multiple range transmissions (usually two or three ranges) and a hydrostatic drive or a gear drive.....that may allow up to 20 to 25 MPH. Foam filled tires are not used much on tractors but is used in skid loaders quite often. Maybe some tractors used at building sites would have foam in them.
Lots of compact tractors have gone to beet juice to prevent corrosion and provide the ballast. It's a liquid and does not freeze at most ambient temps. I've never heard of problems with "FLUID" filled tires....but I can see that solid foam may bounce quite a bit. That said.....at road speeds.....many tractors get a bit squirlly and can be a challenge to drive. The culprit is no suspension, unbalanced tires / wheels, and a relatively short wheel base, etc.
I always think its odd.....that a machine with so much torque has problems attaining road speeds. Speed takes HP. I dont think I have ever had my tractor in high range yet. 10 MPH feels pretty fast in a tractor....lol.