Richardson Lake has some nice paddling with close to zero development with several sandy beaches. You need to make reservations for the remote sites through South Arm campground. It gets far less power boat traffic than Umbagog. Like Umbagog, it is fairly shallow and it does tend to get afternoon NW winds that can cause swells and possibly white caps. For calm water all day, they may not be the best choice unless the forecast is for no wind. The upper Androscoggin has several flat water stretches, there are no formal campgrounds but there is a lot of large timberland owners who will not object to LNT camping. The stretch from Shelburne to Rumford has a minor stretch of fast water near the gilead bridge and one set of minor rapids in Newry. The campground in Bethel can set you up with a shuttle up river and then you camp in one of the primitive sites and then paddle down to one of three takeouts upstream of Rumford.