[Marcello]

Insofar armor goes IIRC each armor point is roughly equivalent to 1 cm of LOS RHA.For example the 45mm plate sloped at 60° of the T-34 has in game value of 9.
LOS thickness can be calculated by dividing the real plate thickness for the cosine of the angle of the sloped plate.In the above case it would be 4.5cm/0.5 = 9.
There are others factors to consider such as armor plate quality and such but the above can provide a ballpark figure.
Insofar speed, size and ROF there are probably design conventions.I would love to hear about them too.