It depends on the monetization model you have in mind.
Are you looking to be an affiliate?
If you're looking to make money through affiliate sales, then pay close attention to the per-unit price of the items you're selling.
For example, if you're thinking of selling stuff on Amazon, keep in mind that different product categories have different average prices.
Since Amazon has been reducing the commission rate that they're paying, average product prices count for a lot.
There's a big difference between an espresso machine that sells for $500 and a handy mask that you can sell for $10 a pop.
If you're only going to get a 4% commission, the initial product price is extremely important.
Start with the product or service that you're selling, and then focus on the kind of questions that people would ask about that type of product.
This should then give you an idea as to the type of site you should build.
You're saying, “should it be a micro-niche or a macro-niche?”
I’ll start with a micro-niche, but the domain name should be a little bit wider.
So, for example, you're starting with a certain type of blender, but your domain name implies that you cover a wider range of blenders.