FWIW, we've owned two American Tugs, a 34 and a 39. While most AT owners seem to cruise at displacement speeds, I can verify from our multiple years of ownership experiences that it is indeed possible to feasibly cruise at low to mid teens, if the boat has the right engine and if you are willing to pay for the fuel burn.
With the AT34, as long as it's equipped with at least 370 hp (or more), you can cruise at 13-14 knots. The boat will perform just fine and handles beautifully (albeit with a wet ride, the hull does throw a lot of spray but that's what windshield wipers are for). Of course you will burn much more fuel at 14 knots than at 7, but it's very doable and a personal choice how you want to spend your money.
In that sense the AT34 can perform and be used similarly to a 'downeast' style boat. As others have mentioned, there are aa great many different types and manufacturers of 'downeast' boats. Some have smaller engines and cruise along at displacement speeds; most are powered to attain semi-displacement speeds or even into the low 20's. There are various hull shapes, soft vs. hard chine, skeg type vs. built-down keel, each with their pluses and minuses.
The AT34 will have more cabin space than a similar length downeast by virtue of it's greater beam. A comparable downeast, like a Wilbur 34 or Duffy 35, to many eyes is a prettier boat. As with any boat, go see a few and see what works best for you.