Thank you for contacting us here in the Support Forum
First let me point to the title of the Post you mention:
"Building a membership site with WordPress – a challenge or a piece of cake?"
The summary of that post is, it's not a piece of cake but its possible, since CRED 1.4
CRED 1.4 supports User forms and with this you can let Users create and edit User Profiles from the front end, the missing piece to Membership sites.
A membership Plugin would in my opinion not be necessary if you are using CRED.
CRED Commerce currently does not support payment if a new User is created, but you can workaround it by using the current supported payment of form submission:
https://toolset.com/documentation/user-guides/using-cred-commerce-to-add-payments-to-forms/
You will be able to customize the BuddyPress pages with Toolset (specifically, with Views).
Since these are hard-coded PHP templates, you will probably need to do a tiny edit in their PHP, to insert our Views. You can insert Views to PHP templates with a single line of code, as documented here:
https://toolset.com/documentation/views-php-integration/
Then, you continue the development in the WordPress admin, by editing that View.
Access will help you to hide content by User Roles, Specific users or Custom Access Groups.
I have recently built a site where the entire WebSite was only accessible if Users are logged in.
This required a single special PHP template (if user is not logged in), but it was only needed because I used a Static Homepage, and Access can not hide Static Home pages.
I could help with this specific PHP template and how to use it in your theme.
I achieved the goal of that Website with Toolset only, and some Custom PHP specially the mentioned "not logged in" template and some Custom CRED API codes, which you will most probably not need.
Please let me know if you need any further help with this.
Thank you for your patience.