Install WP in the root directory or subdirectory?

I know we can use either root directory or subdirectory, but I am just wondering which one is more suitable for my website.?

Basically my website also contains some webpages other than WP blog posts. ?The thing is that I want to take the advantage of the WP users, and all these webpages can use WP cookies to recognize the WP users.

There are two designs.?

1. Install WP into root directory and the URL will be something like: https://example.com/

– Customize the home page(get rid of the posts and it will looks like a normal website home page).
– Create some non-blog pages (e.g. https://example.com/product) which are able to read the WP users cookies.

2. Install WP into subdirectory and the URL will be something like: https://example.com/blog

In this case, my other web pages including home page do NOT under the WP Installation directory (https://example.com/blog). Can these pages use WP cookies, users, and database tables?

The other question is that should I create the non-blog webpages within WP or separately?

I really appreciate any advice!