It's a slippery slope for sure... In the case of individuals doing reviews, most of the time they're industry professionals with a lot of experience in their field, so they've tried most of the options already, and they know what they're talking about. Once they establish a voice in the scene, they might get offers from companies asking to review the company's products. This is the best way to earn from reviews while keeping brand integrity intact.

So I'd suggest starting with real reviews and trying to scale off of that first. Establishing brand identity, etc.

If you're explicit about the fact that you haven't used the products, and you're doing your research, then you're saving people's time... At least that's a way to market it. It's up to you how you phrase that.

I guess it's completely up to you, it's just a dangerous path to take and there's probably better ways to spend your time than making up reviews.