Does a longer kayak have a higher load rating?

No. It's the total for paddlers and gear together, so leave margin for a cooler, tackle or a dog, and follow the model manual; none of the ratings says a hull suits rapids or open water. Among the solo boats, the Pungo 125 is rated 375 lb and the Pungo 120 325 lb, and the Pelican Argo 100XR is the lightest listed boat at 40.7 lb.

It matches the exact rating rather than a minimum. If you choose 350 lb, you'll see only the Tribe 11.5, while the Aspire 105, Pungo 125 and Cove 14.5, which are rated higher, drop out. To see everything rated at least that much, leave it on Any and read the column. Not consistently in these listings. The 168 in Perception Carolina 14.0 lists a 300 lb maximum capacity, while the 126 in Wilderness Systems Aspire 105 lists 400 lb, the highest published rating among the 11 solo boats here. The sources do not establish equivalent capacity-test methods across brands. The Cove 14.5, the only tandem, is rated 550 lb but weighs 73 lb.

Ten of the 12 are sit-inside. If you want a sit-on-top, Perception's Access 11.5 and Tribe 11.5 are the two options, and they're the heaviest and widest solo boats here, at 55 and 58 lb and 31 and 30.25 in wide. Perception's day-touring Carolina 12.0, Carolina 14.0 and Conduit 13.0 are the three narrowest, at 24.5 to 26.5 in.