Ogunquit Maine is worth a look and on route.
Conway and North Conway are distinctly different towns by the way. I'm guessing you mean North Conway. Conway is fine location wise but nothing much to see as a town. Which ever mean you'd want to drive the Kancamagus Highway from there if you're interested in scenery.
Not thinking of going farther north in Maine? You could look at the TA introductions to Freeport, Boothbay Harbor, Rockland, Camden, and Acadia National Park. You have quite a bit of time, and could consider doing several nights in or near Acadia (which is spectacular).
What are your goals? What kinds of things do you like on vacation?
Also, once you get to about mid-September, just be aware that now you are in "leaf season" and many inns and hotels will require multi-night stays. That may perhaps not be the case along coastal Maine, I'm not sure. But will be true in the inland New England areas where it becomes a very popular tourism season. What are your dates?
Thank you will do
Thanks will do
"Would Portland be a good place to stay as a base?"
Not knowing what your interests are, 3 days in Boston + 1 for Salem; then 2 days for southern Maine; 3 days for Boothbay Harbor and Acadia; 3 days for White Mountains - that's 12 days, plus consider travel days - some of the transits will be 3-4 hours of driving.