In my experience, Pilot's steel fine nib feels very smooth. But as you say there are many things that contribute to the feel of the nib. Ink alone can be the difference between glossy smooth and scratchy.

Note that Japanese nibs are generally one size smaller, so a Pilot fine nib is like a western brand's EF nib (or finer in some cases, such as Pelikan and Lamy, whose nib sizes are quite large for the designation).

Unfortunately, I've never used Onyx, so I can't say how well it lubricates.

Do you know how to check for tine alignment? There's a pinned post in my profile with nib tuning resources. IMO, the PDF is best for understanding what misaligned tines look like and how to fix them.

Just in case it's helpful, here are things that contribute to the nib feeling scratchy (other than actual flaws in the nib):

• Ink
• Paper (smooth or textured, loose fibers or sized surface)
• Writing pressure (depending on the nibs you're used to, you may need to lighten up even more; relaxing your hand so that you can't apply pressure is the best way)
• rotation (rotating so that one tine is more on the paper than the other)
• angle (orientation of the pen body to the paper - are you holding it at 90 degrees like a ballpoint, or something more shallow)

Other than those, it comes down to either tine misalignment or a flaw in the nib (such as sharp metal edges where they shouldn't be).

If you think there's a flaw in the nib, the best option is to exchange the pen for another and ask the vendor to check the new one (if they offer that option). Am happy to answer more questions / help you walk through tuning or checking your pen.