File upload experiences

I am building an app where users can upload images, video, docs or even audio from web or mobile. I am curious on general strategies, learnings from people who have implemented it in a React-Redux app - did you upload directly to S3, or via FileStack or Transloadit? Any libraries (like Uppy, or FineUploader) or processing services used? Did you support chunking or resumability?

Any experiences are much appreciated!