I was an engineer at Amazon for a couple years (left about a year ago) and I've never heard of anybody using these services. It's possible that some of the services that we used internally were simply frontends for those AWS services. Having an internal frontend for an AWS service was common.

Yes, WorkDocs is used extensively for document sharing. Chime is the go-to chat/meeting/VC app. People use WorkSpaces when they need a Windows or Linux test machine.