JFETs aren't fundamentally different; they are selected based on testing. When you buy a, say, PN4392, you're buying a part that was tested to a switching spec, so it has so-and-so pinchoff voltage, Rds(on) and leakage.
You can infer the small-signal parameters from Vpo and Rds(on), if a bit sloppily.
A 2N5486 may not even have an Rds(on) rating, though it's pretty obvious what that value is from the curves. It will however carry the assurance of so-and-so transconductance, capacitance, Y parameters, whatever, that you need in the design of an RF amp/osc.
And some RF parts may carry a noise rating, but noise depends on frequency too; expect 1/f or popcorn noise at low frequencies (audio, LF). Conversely, low noise (LF) parts may be noisy at HF, though they're sometimes too big (e.g., J105) to use at high frequencies anyway so that's okay.
There are very few JFETs that you actually need/want, and this is reflected in the ever-shrinking market. They're great parts when you need them, it's just very rare that you do.
Tim