Yeah the vows of lower tantras are certainly less severe; I don't even know what they are, and it's hard to find info about them lol. Perfect Conduct may explain them, but I have not read it yet.

For inner tantras/HYT, they're explained in some cases, but a lot of the time, you are just expected to know that you need to follow the 14 root and 8 branch samayas. Samayas are technically not even really supposed to be discussed until one has the empowerment, which is kind of messed up, but we are lucky that we have the internet and books that explain such things well.

But even for such things, in my experience, many teachers are very lenient with their students. They know that there is no possible way that new students can understand all of these things, and they try to encourage students to relax and take away "the main focus", essentially. Just like how Garchen Rinpoche always focuses on the main idea of samaya being Bodhicitta.