What are the differences between workspace .json files?

Which from the following workspace files are used on desktop and on mobile?

workspace-mobile.json
workspace.json
workspaces.json

I have a separate config folder for my vault on desktop and android. Which of these files need to be kept on which instance, and what files are safe to be discarded?

Don’t need to discard anything. Let Obsidian keep hold of what it wants.

The workspace-mobile.json is, yes, you guessed right, for mobile. Mobile workspaces are different from PC ones (PC workspaces are more advanced). It holds the last state of your workspace you left it.
The workspace.json file is the same for PC: the last (current) state.
The workspaces.json file holds all your workspaces, in case you have been using the Workspaces core plugin to save various workspaces. It can hold one workspace or more.

I’m guessing (it would make sense) workspaces.json can hold both mobile and PC workspaces.
I’m using dedicated .mobile and .pc config folders, so I don’t need workspaces.json in the .mobile config and the mobile one in the .pc config.

That was the answer I was looking for. I initially just copied one config folder and made them two different configs for mobile and desktop, so was looking into which files were made obsolete due to their divergence.

P.S desktop workspace file in mobile config and mobile workspace file in desktop config have the same modified date which is about when they diverged, so they’re no longer used. I’ve deleted them.