use of a Nitrox regulator vs. normal air

[Slamfire]

I'm not completely aware of the detailed internal regulator structure, but are the conventional air regulators lubricated somehow? If yes, I guess that will be the difference between air and Nitrox certified regulators.

Lubrication is one difference. You must use O2 safe lubricants like christolube. Oring material is another difference. Regulators for high O2 content should use viton orings. Also, titanium regulators are not a good idea because they do not like high pressures of high O2 concentrations.