WordPress with separate landing pages?

Getting my brain tied in knots over the following.

I want my home page https://www.domain.com to be a landing page with a sales letter to sell my product. This is a clickbank product with 2 upsells. So when the person buys the product, they get taken to another page https://www.domain.com/upsell1, then after that another page https://www.domain.com/upsell2 before finally being taken to the thank you page where they get their logon details for the members site.

There will be a members area with each of the products in there that they have access to. Also on the site menu there I want a blog, and any other stuff I may later put on there (the blog is obviously open to anyone).

My question: am I best installing wordpress into https://www.domain.com/members and building my members area and blog from there and making the landing page on https://www.domain.com separate from this, or can I still make this work nicely if I install wordpress in the root directory?

I want to be able to create my own landing page outside of wordpress and not be required to have it as a wordpress page (unless there’s some particularly amazing landing page plugins of course that I can make it work with).

Thoughts?

Thanks in advance.