A little late to the party but here's my .02. As background, the PL14459 app is what Honda used on 90's model Accords. The 7th gen Civics and now Accords went to the slimmer PL14610 app. In 01, though the Civic spec'd the slimmer filter my local dealer still sold the shorter fatter PL14459 app. that has the same gasket diameter. Then, they finally went to the PL14610 app.
I'm not as quite particular as you about the 20um vs 40um rating of the PL14610 which I use in my Altima, Accord and daughters Civic. As AE alluded to, real world difference likely not very significant. Heck, right now I'm running an Advance Auto Total Grip on the Altima, Civic and a Tacoma, which is rated 96/94% (single/multi) efficient, likely at 20um but it doesn't specify. But $1.45 for a well made Puro filter, with the added benefit of texture, I'm not sweating it. In comparison to that, I know any new P1 or Classic is doing a good job.
In the 2.5L Altima, the filter is just above the oil pan on passenger side. Sounds like the same as the 3.5L. I think one time I removed the filter by turning the wheel to the right (didn't remove shield) when I changed the oil without using ramps. For me, it's just a lot easier to get to drain plug by putting it on ramps. Plus, I feel like I might be draining a little more oil out with the plug at the back of the pan, but that's more placebo effect.
But to the topic, the PL14459 should work fine and I expect it has a somewhat greater oil holding capacity than the slimmer PL14610. I don't know of any longer app for the PL14610.
