Mount Washington is a great place to visit; probably not a great place to consider flying. You should expect very high winds and probably flight restrictions.
I've only been to Maine once, and not with a drone. That being said, if you like flying tight quarters along a stream or other waterway, there are lots of lovely (but small) waterfalls, old water mills, and just wonderful scenic places along the way. Maine has LOTS of trees, so almost everything you want to see will be at risk of getting hung up or obscured by the trees. Many folks go there in the autumn to see the maple forests "fall color", which is truly spectacular.
You ought to practice some photos now with different filters just to see what captures those colors best. Every sunset will be a good practice shot.
Then there is the coastal areas. Great scenic vistas, lots of wonderful New England charming structures to capture in their rugged settings. Lots of waves crashing on shores, that kind of stuff.
When I went to Maine, we were restricted by the need to go too soon so as to return the kids to school, so we missed the spectacular color. The camping weather was wonderful. I found that most of the great scenery around the inland lakes was pretty much obscured by all the trees. If you weren't right on the shore or in an area that had been cleared by mankind, you really couldn't see too much. I think the drone at 300' would provide a fantastic improvement in your appreciation of the area and your trip.
Despite all the fantastic forests and what should have been great scenery, I often felt almost claustrophobic due to the density of the vegetation. Of course, every highway occasionally opens up with yet another spectacular vista as you crest the hill, and it quickly devolves into watching the forest go by.
Be sure to allow lots of time for stopping! Far more to see if you can just slow down and pick out the jewels. Race through like I did, and you just get glimpses of what you might be missing.
