Is there ANY way to backup or copy the preferences in adobe premiere?

Adobe does offer a basic backup function with syncing to your CC account, but I will say it isn't as thorough as it needs to be. I've had to do this many times as a means of replicating the same config. in multiple workstations that have different CC accounts.

Here's where I'm confused though. Media Cache isn't a configuration. It's equivalent to cookies on a web browser. It makes certain operations faster (usually). It probably wouldn't even work or be of use on another machine because (I'm assuming) that cache operations are specific to that machine.

Not sure what you mean by 'audio config', but let me just say that any Premiere-configuration items are in one of two folders (here's the PC path for reference)

If you've never synced settings to your CC acct.: \Documents\Adobe\Premiere Pro\X.0\ Profile-<Username>

If you've synced settings to CC at least once. \Documents\Adobe\Premiere Pro\X.0\Profile-CreativeCloud-

Now I will outright say how silly the two directory-system is, but I digress. Within those folders are all sorts of things:

.kys files tor Keyboard Shortcuts, .sqpreset files for Sequence Presets, you name it. I could go on all day, but just dig through that folder and you'll eventually see where things are. Keep note of what folder they live in, because in order to be replicated on another machine that same folder structure is needed.

Then you can copy those files to backup, another machine, etc. I like to copy the entire Profile folder to my CC Files manually for a manual backup, and this has helped already on one occasion this year.