I have multiple domains with different content on both, can I use the same user ID and different channels for the websites and still be in compliance? Or can I only have one account per website?
You can use the same with different channels. I don't think it is a good idea to have many different accounts for different websites. Google identifies the ads which are related to the content of the particular website and displays the relative ones. Use channels to track the performance of the ads. Good luck.