What affects the speed in which videos load when using hidden services on TOR? I encountered websites where videos aren't playable because they don't load or buffer and websites that have videos that are playable. I am new to using TOR and would like some insight on video streaming for TOR. Is it due to my internet speed? Is it even safe to be watching videos on TOR?
The speed that videos load at depends on your internet bandwidth, the website's internet bandwidth/load, and the bandwidth, latency, and performance of the relays in your circuit. Yes it's safe to watch videos in the Tor Browser as long as you don't install extra extensions/software (such as Flash Player).
If a video is loading slow, you can try using a new circuit.
If the video hosting is inside the Tor network, i.e. via dot-onion address - it's totally OK and suffers no performance implication if the server is set up as it should be. Take a look at IPFS and ZeroNet - it can also help. The only possible problem can be a live video stream, so as in a clearnet Internet