Do you think that's reasonable to add a subscribe form to a website that's basically a 3-product review website?
I wouldn't do that. Your landing page's purpose is to get the visitor to the merchant's page and nothing else. Give only one exit for your visitors.
Yes i would highly recommend mikey 1090 that way there are no distortions and if they do click away you still have the chance to capture their email and build your list Just make sure you are giving away something of value to capture their email.