Pipes with NW dimension
DN just means "nominal" diameter as opposed to actual diameter.
NB (Nominal bore) is the same but is an older term.
DIN is manufacturing standards from Germany, many of which are the same as BS or EN standards but there are some products which are specifically made to DIN standards without there being an equivalent BS or EN. Often encountered in processing industries.
NW is a new acronym to me but as far as I can tell is standard dimensions for Vacuum fittings.
https://www.mcmaster.com/products/nw-tube-fittings/
Revit allows you to designate actual inside diameter, actual outside diameter and nominal diameter for any pipe type and you have freedom to designate these to your needs.
For example for steel and iron pipes it is usual to designate the pipe by nominal size for example 15mm, 20mm 25mm etc rather than actual bore or outside diameter:
For copper and plastic pipes (in UK and EU) it is conventional to designate them by their outside diameter and in Revit this is done by making the nominal diameter the same as the outside diameter:-
So you can set it up whichever way that you want.
INTERNAL diameter is the one which matters for pipe sizing and pressure loss calculations.
Regarding fittings and accessories, the pipe connectors always read the pipe Nominal Diameter and then if you want to instead set different diameters (for example actual outside diameter of a fitting, wall thickness etc) that would be done by means of formulas or lookup tables.
I found this site for high vacuum BIM/CAD families but you may have to create your own (or modify existing families). Often you can get a 3D CAD file which you can import into a Revit family and then add connectors and informational parameters to make it function (sort of) as a Revit family.
I've no idea if my reply is helpful to you but if you need more help reply back.
