Can we have an SSO login method for OAuth or SAML setup that requires that we authorize the site accounts before they can see any products or pricing?

If you are using an SSO method of login on your site, and a client who exists on the identity provider system logs into your Pressero site, their user account will be created on the Pressero site. 
But when a user logs in on a Pressero site using SSO login, they will be part of a Site Group that is specified on the identity provider system. Products and Pages created on your Pressero site have settings that determine what Site Groups can view those products and pages.
If the Site Group that gets assigned to new SSO logins on your site does not have any products, pricing or pages available to them, they will see just the basic content of the site.
The site will generate a new user email notification if a successful SSO login happens. You can use this process to see who is logging into the site, and then grant them access to products and pages by changing what Site Groups the new user belongs to.