Sorry I don't know what you specifically mean by "porn streaming" are you talking about a dedicated app for a specific streaming service?
If so, I highly doubt Apple would allow those on their platform but I've never actually checked. There are semi-sketchy IPTV clients that you can use to watch what seems to be unofficial streaming services, so perhaps those can also be used to watch what you want?
As for VLC, it's open source I encourage you to do your own research as I can't answer your codecs question with confidence.
Well if I watch porn I don't download it and watch it later, but open some place app or website and browse videos on my TV to fap to comfortably from my couch.
To be fair my question is already answered, no porn support. You need a another device to stream from.
You can also use Plex to access a media server with whatever you want to put on it.