if you go NOBO you will have a many options for great camp spots, water sources, and views on the north side of the notch once you have climbed up to the speck pond area. Speck pond camping area (AMC run) is VERY beautiful and if you sealth camp you will have even more options. South of the notch has a very limited places to stealth camp, water sources and tough to find views because the thick evergreens. I recomend this because after a fun day in the notch you can go swimming on a mountain top pond.
though it is southern maine it is still very remote, if you are using your own car it’s ok, but if you are on alt. transportation you may want to consider how you are getting to the trail and getting off. I think it’s easier to have a ride to a remote area and hike back to town than vise-versa. with this in mind, it will be better sobo because you are walking to gorham,NH (has alt.trans.) and not to andover,ME which is tricky just to get a paid shuttle ride out of.
Happy hiking!
magic