This article might be interesting or make things more complicated 😉
The four busses you spoke of can all be the same thing. That is, because all busses do the same. They are a channel in which other channels are mixed into.
Stereo- or Two-Bus got their names because all other channels on a console are mono channels. I wouldn't use those names in a DAW.
Well, Stereo-Bus can have a different meaning in a DAW because you can switch a Bus between Stereo and Mono.
The Mix-Bus is the one where your mix comes together. I would call the Main-Bus the one with the Outputs out of your DAW. So often those two are the same.
My guess is that you hear Stereo-Bus oder Two-Bus more from PLAP members mixing with a console and Main-Bus or Mix-Bus from members who are mixing in the box.