Ahh uno. What a game. I had a good friend absolutely lose it when I played a draw 4 card and he had to draw 16. I initially thought he was just putting on a good performance and was laughing along with it but then he disappeared and didn't come back and his gf had to embarrassingly explain he was actually pissed off lol. That was a shortish cards night. Monopoly and pictionary are other games I've seen people totally lose it on. Especially with couples playing pictionary
In regards to the question, how I play is you can draw one card and then use that card if playable but not the one you're already holding. I once played with some people who had a stupid rule that you could just keep drawing cards. That was really annoying