Nick,
A lot of it depends on who is using it - private farmer or custom/for hire, and the state in which they operate. We retired to Missouri to my wife's family farm and I work part time for some farmers. They have two combines and a corn head and draper head for each. They farm a little over 5,000 acres, spread out over two counties. So, that entails a lot of moving of equipment. They have several header trailers, none of which have brakes. I believe the 16 row corn heads weigh right around 12,000#. I'm not sure what the drapers weigh. That means having both heads at a particular place, as they raise both soybeans and corn, (and sometimes wheat). When we move, it's usually two combines, four heads and trailers, a tractor and 1000 bushel grain cart (sometimes two), and four semis. Mostly, it's just a few of us moving a few machines at a time so it doesn't all look like a circus parade. If that is a custom outfit in your pic, I can't imagine they would have the fuel trailer full, but could be wrong.
To drive a farmers's tractor/trailer in Missouri, no CDL is required within a 150 mile radius of the home base and it's not for hire. I'm not sure what you are allowed in other states. Also, during harvest, we get a 10% overage on weight, so can be legal at 88,000#. Personally, I'd like to see drivers required to have CDL training...
Bud