Most of the game carts have stamped or cartridge type bearings on their wheels. Those type bearings wont survive hard use or speeds much over walking speed.
The cheap steel rims with solid rubber tires are heavy.
Game carts come with 3/4 or 5/8 inch axles. The 3/4" being much stronger.
The pressed bearing, solid rubber tired game carts leave much to be desired.
Its important to consider tire size. Larger diameter tires roll over rough terrain easier.
I run the Cabela's Super mag hauler game carts but replace the wheels and tires with plastic mag wheels that take stainless sealed bearings and use pneumatic tires.
My game carts are significantly lighter, roll easier across rough terrain, can haul more weight than one should try to pull, and don't wear out quickly.
My source for those parts is no longer available, so I wouldn't know where to point a guy. The 20" mag wheels on Northern Tool look similar and likely a guy could substitute bearings with an internal bore of 5/8, or maybe even 3/4. A person would have to know the hub inner diameter to see what was available in bearings.
Its also helpful with game carts to add sides of some sort to keep your load from getting into the wheels.
I made a tongue that easily bolts onto my game carts and allows them to connect to my mt bike at the seat post so they can be used as a trailer when going in longer distances on gated roads.
But if that's your intended use you'd be better served to just get a bike trailer to start with.