NExx are Suzuki OEM. 3 tapers, progressive from lean to rich.
N3xx are Yamaha and KTM OEM. 2 tapers only.
The first taper of both are similar, however generally speaking the N3xx needles to be run in a richer clip position or else it falls too lean in the mid (at the end of the first taper). The transition from lean to coming back into fuel on the second taper makes for a stronger 'hit'. The added fuel from a richer clip position means the bottom end makes great torque. So, N3xx is generally a very strong setup - often too much for the average weekend warrior.
The NExx has less variation between the tapers due to there being a 3rd. It also adds more fuel towards WOT (is noticeably thinner to the naked eye).
The straight sections are similar length. The diameter effects up to around 1/8th throttle in conjunction with the pilot, slide, and air screw.
The difference between an N3EW and N3CH is that the N3CH is half a clip leaner, and a step richer on the diameter. If they suggested running N3CH#3 you could try N3EW#3 and it would likely be similar off idle, a bit richer between 1/4 to 1/2 throttle, and not a lot of difference into the top end. It does require a larger main than the NExx needles comparatively due to the taper.
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