Are you talking about arrowhead?
From Arrowhead to the trails requires driving on actual roads (well just gravel things that resemble roads but they count) so you need plates/insurance but you can run them aired down and without sways no problem.
Lots of the sites have room for a tow vehicle, I usually take both a jeep a tow behind camper thats about 24' when it's setup and another car for the wife and that all fits in one spot no problem.
If you weren't road legal I've seen people camp at the entrances to trailheads all the time, theres a spot I want to say down at the falls dam south parking area that has a spot I've seen motorhomes pulled into (no hookups there but also no camping fee's or real roads to drive on to get to trails)