Source Bus vs Sound Class?

Is the Source Bus intended to replace Sound Class? Or are they different?
Can anyone give a use case for each and explain the advantages/disadvantage?.. or if there is a place where all of the features of the new audio system (including how it interacts with the old system) is clearly documented with use case/examples/example projects that would be the most amazing thing possibly ever in the entire universe (no hyperbole there, i swear).

Sound Classes are an arbitrary LOGICAL classification of sounds allowing you to perform logical mixing operations (attenuating volume or adjusting pitch en masse). There are a lot of other parameters that are set on Sound Classes which result in a weird conflation. Sound Class mixing actions are performed via Sound Mixes.

If you were to draw an analogy to your DAW, Sound Classes and Sound Mixes are like VCA groups. They enable automation on your sources logical volume amount en masse.

Source Buses are literally buses where you send actual audio to and from–they let you mix multiple sources together (literally rendering them into a single buffer of audio) and they allow you to treat them as if they are sources in the Level, so you can spatialize them and apply source effects on them, etc.

The DAW analogy of this would be like an Aux Bus that has its own fader and pan pot.

ok, that makes sense. thank you, dan!