How to know how many bits the file is

If it's for social media, I'd say that it is not worth it to maintain a 10-bit workflow.

If the finished edit is the product (let's say an episode of a television show or a feature film), then yes it is worth maintaining a 10-bit workflows.

The answer ... you might have expected ... is ... definitely, maybe.

A larger bit-depth and less compressed file will (depending on the upload processes used by the service, which can vary some depending on region or something) tend to appear a little better on better quality screens.

But will not be any different on many screens.

So will your viewers be on a phone or a nice big TV or monitor? And what kind of 'net connection will they have?

I know a fair number of folks who upload ProRes or DNx 10-bit and very low compression files to attempt to get the best possible final image after YouTube/Vimeo/Whomever re-compress the file, which they all do to all media uploaded to them.

And many others that just send a moderately low compression H.264/5 file.

Your choices are many. And the answer to about any question ... is ... maybe? So test all sorts of things.

Neil