I drove my FWC from Boise to Maine in 2017. Loved Maine. Spent several weeks around Moosehead lake paddling and hiking. Lots of hiking trails. Greenville is at the southern tip of the lake and while a very small town it has a good grocery store and plenty of outfitters. Dispersed camping is limited in the Eastern states. Maine has some Public Lands which allow it with a few spots on Moosehead lake. Closest to Greenville is about 8 miles up the West shore road. You can get a Public Lands map at Northwoods Outfitters across from the lake. It has a nice cafe inside with WiFi.
Going up the East side of the lake you have to drive 20+ miles for free camping and there are only a few up that way but those all have fir pits, outhouse and usually a campground host. There is also more wild life up that way, where I saw moose every day.
I then spent three weeks in Acadia National Park. There is no free camping there, or anywhere near it. I found the best deal at Bass Harbor RV park where camping sites are more private than the Park campgrounds and end up being less expensive because they include showers and has a laundry, rec center. Hiking and paddling in Acadia is second to none, IMHO. But the Park is an "urban park" in that it has lots of little towns and villages so is not wilderness in any sense and for that reason some do not like it. What I liked was I could get up at 7, hang out at a nearby cafe for a couple hours, get to a trailhead by 10, hike until 3 or so, maybe hit the beach or do a short paddle, get a lobster roll from a food truck and head back to my camper. There is also an extensive free shuttle connecting villages, trailheads and beaches. Also fantastic sea food restaurants and some night life.