Interact with an overlay extension?

Are there any differences between overlay, component or panel extensions (except the placement)?

Is it possible to interact with every type of extension?

Dimensions and placement really.
Overlay has some extra things to consider like, you need a transparent background for msot of the stream so viewers can see the stream/you don’t cover the whole thing, but that might make sense anyway depending on the use case

Not sure what you are asking here.

A given extension can be active in a single slot only (mobile is always the same slot regardless of the desktop slot).

Maybe @alexL meant to have some kind of interaction with chat or subs to reflect a global change into the overlay extension?

Sure, you can detect if a user is a sub and do something different.

or you can read chat and do something in the extension.