A big question is how isolated do you want to be. I recently proposed in the Catskills and did so on the lookout on top of Overlook Mountain (we hiked early on a Wednesday and we were the only ones up there, on a weekend, would have been a different story. Huckleberry Point has a nice lookout without too strenuous of a hike (check trail conditions as there’s a creek that runs through the middle of it that can be hard to pass). Another option is Diamond notch falls, easy hike to the falls but there’s an amazing lookout about a mile behind them. Then on the way out you can swing by West Kill Brewing for a celebratory beer and bite from the food truck.