Not sure I’ve never tried to do what you want to do. Most of the things I’ve dabbled with are too heavy for client side, which means punting it server side and then out of date/way out of sync.
But depends what sort of interaction you want from viewers. I was just thinking you were making a pretty overlay which wouldn’t need/have any interaction (except maybe picking which filter)
On second thoughts what you describe sounds a little like the SnapChat extension, but that will be running a local compoenent to inject the “cat ears”/whatever and access the video stream locally and then thats in the live stream. Which is probably the most performant/works on all viewer computers.
I don’t think that an extension is able to break out of the iframe to see whats behind it, might means you will need a local component to capture the video/display on the streamers computer.