Scotland Level 1 says: "After Setup, in Coastal lands, Explore Cards add 1 Town instead of 1 Explorer. “Coastal Lands” Invader Cards do this for maximum 2 lands per board."

The maximum of 2 lands per board exception only applies to the specific "Coastal Lands" Invader Card, found in Invader Stage II. Other Invader Cards, including Stage III cards, can add Towns to more than 2 Coastal lands on a board.