Good list!

While looking through it, I realized that as a newsletter subscriber, I prefer #3 on that list.

Personally, I often don't really like receiving affiliate marketing emails or emails with ads for other companies. When I subscribe to someone's newsletter, I feel like I want to hear from them. So I don't mind emails about their own courses and services but if it's marketing for other companies or products, it sometimes can feel a bit forced unless it's done very tastefully and well.

I'm sure a lot of that is niche-dependent, though. I mostly follow people in self-growth etc. which feels like a very personal, relational niche. If someone's target audience is pet owners, it's probably very easy to showcase products from other companies without running into the same problems.