The H&R teflon lined bushing, for the front bar, is a direct fit, and I recommend it over the factory original front bushing. The rear bushing is either the H&R with a spacer, or a bored-out factory bushing, like BMinFSL did.
Changing to the stiffer H&R bars will certainly reduce roll, with air suspension or steel springs. I don't think the effectiveness of the bars is any different whether you have air or steel springs.
Concerning the aftermarket bar options, the solid H&R bars are the only real choice, as the other vendors only offer hollow bars, which I think are not much stiffer, if any, than the factory bars.
Although the 034 rear bar is solid, they don't offer a matched solid front bar. Plus, my prior vehicle experience with an 034 rear bar (on and Audi Q3), is that the paint finish is not as durable as H&R, resulting in a completely surface rusted 034 bar within 3 winters. The finish and manufacturing quality of the H&R bars is top-notch.
I don't think there is any worthwhile performance advantage for the aftermarket endlinks, the Porsche (or Audi ones) are not exactly made out of silly putty.....the helm-joint (ball joint / spherical) aftermarket ones are expensive, and will wear-out and start rattling within a year or two. As far as adjustability, unless you are a track junky, and need to corner load or asymmetrically bias your bars, you don't need that feature.