The Coaxial D-Sub have like the Power D-Subr replaced the two rows in a Standard Density connector with a coaxial contact that take up about the same size as the two rows of signal contacts. The Coaxial D-Sub is exactly the same size as the Standard Density connector but instead of example 9 positions of signal pins it has 2 power contacts , or instead of 37 positions of signals it has 8 coaxial contacts.
The Impedance for the coaxial contacts are 50Ω or 75Ω
The Coaxial D-Sub with Mixed Layout mixes both coaxial contacts and signal contacts in the same connector. For example the same size as a 15 position Standard Density D-Sub you can have what we call a 7W2, which means there is 7 contacts where 2 of them are coaxial contacts, which means there are 5 signal contacts, so 5 signals and 2 coaxial. See the Layout in the Tech Specs on the bottom, there are a lot of combinations of the Mixed Layout alternative.