I have no knowledge of NJ in particular, but presumably like every other state they have a website for their state parks that lists the features, rules, etc. That would be the place to start. You can of course call the number listed for a specific state park in which you're interested to get more details.

If NJ is anything like Oregon, they won't allow camping outside the regular campgrounds. We do have hiker/biker sections out here, although that means you can't bring a car into the park. You can still test your gear and your techniques, although I'm quite sure that park management would prefer you to use the restroom rather than digging a cathole!

The NJ section of the Appalachian Trail might be a good place to investigate.