Would 17' be too long or
would something shorter do better? I've been looking at boats in the
15' to 17' range. Primary use would be open water but there are some
nice slow but smaller rivers in the area that would be nice to use.

WRT New Jersey Rivers, including the Delaware which is quite wide,
most people I know here who began with longer touring boats ultimately
bought boats no more than 14 ft long. Maneuverability was paramount and
with a moving current the longer boats became a liability. It's not just
the ability to turn the boat readily. Pine Barrens rivers, for example, are
often narrow and some of these longer boats simply could not go around some
of the bends easily, especially in the hands of a novice paddler.
Overhanging trees or other strainers are also difficult to deal with in a
long boat.

JP