Two separate questions.
You are asking how the spell slow interacts with two totally different features from different classes, that do different things, and I can't really see that there is any overlap in how those features work.
These are good questions, and I can't find any duplicates on the site.
My rule of thumb is, if I can make the question clearer by rephrasing two or more queries into a single question, then I should do that before posting.
If I can't make it clearer by reducing it to one question, then I feel it would be clearer as two posts.
The alternative to splitting unclearly combined questions is potentially multiple partial answers and/...
It depends on the questions you have about it. Your questions should focus on one specific problem you're having. That usually means one question per question, but can sometimes closely interrelated questions can be asked together.
Our Q&A system's default is one question per question. We work best when you ask a single, discrete question to which people ...