No idea of your time frame. I can keep you in Maine for six weeks.. ( I live there) or six weeks in Nova Scotia ( done that too)
I don't care for PEI.. too farmy. The Confederation Bridge is one way toll and expensive. Toll is collected westbound.$47 for two axles $8 for each additional axle.
I suppose it was the cheesy outlet mall on arriving at PEI that soured me... We drove from there down the coast and returned on the ferry to NS from Wood Islands PEI. The Round trip on the ferry is over $120 round trip but one way fares are available to Caribou NS from Wood Islands. They do charge by height!
Just an advisory.. We did like the drive down the coast but did not camp on PEI. Lots of red clay and lighthouses.
If you want to skip Maine ( and Bar Harbor in June is not yet jammed) consider the ferry from Portland to Yarmouth NS.
https://www.ferries.ca/thecat/fares/
I have a preference for the Cape Breton National Park campgrounds..