It sounds like we paddle the same type of water and have the same focus on weight and well-behaved hulls.
As Marshall said, tracking is a function of hull shape, not length. For a given hull style, a longer hull will track better, but that doesn’t mean all short boats track poorly. For what you want to do, I’m guessing 14 feet (or even 12) is enough length if the hull tracks reasonably well.
The skis and fast touring kayaks mentioned above are all good boats and light, but not necessarily well-suited to the water you want to paddle. Plus they will be a step up in skill required and are NOT a good loaner boat for visitors with no experience, one of your intended uses.
I tested the Epic GPX, a nice boat. The design and paddling is really good. but I found the deck too low - I had to sit with my legs mostly flat, can be difficult with knee/hip/back problems.
I’ve paddled and like Lincoln kayaks but never owned one. Ditto for Eddyline.
My lightest and best tracking boat is a 13’9" skin on frame Cape Falcon SC-1 (early version of the current F-1), weight about 33 pounds. It has a skegged stern and glides amazingly well, SOF is more durable than you might think.
A pack canoe would do well in the types of water you want to paddle. They can be extremely light, there’s a wide variation in styles and price points.
Folders (e.g. Pakboat Saco, 12.5 ft, 20 pounds) and performance inflatables (e.g. Sea Eagle 393rl, 12’10" 35 pounds) are also an option.
Now that you have a long list of possibles from all the posts here, I suggest looking for used boats here on p-net or the local classifieds. I started out trolling the used listings here, then looking up the boats for sale that seemed interesting - you’ll soon get an idea of what’s out there and what you might want. Often a used boat that you’re not happy with can be resold at cost, sort of a no-cost rental to try things out.