Gun customization

[Impact]

A few questions: What units are used for convergence setting? Meters or yards?

Is there a list with all the ammunition types and specifications for each one? For the 20 millimeter cannon of the Luftwaffe, there are Panzerbrand grenades, Brandspreng grenades, Brand grenades. What are the differences between these incendiary types? (I am german, I know what the names mean)

Whats the difference between phosphor and elektron types of incendiary ammunition?

Is there some documentation about those used in the flight sim?