Hey @abdurrehman,
Be advised that the built-in Portfolio custom post type, when enabled in the Theme Options, you will have to create a NORMAL page and then use the Layout - Portfolio page template to display the Portfolio archive page. If no page is assigned with the Layout - Portfolio page template, the portfolio custom post type archive page will just use the default blog archive layout.
Since you want to create a custom Portfolio archive layout, you have to go to the Layout Builder builder and create the archive layout. A condition must be set like the “Post Type is Portfolio Item” to assign this newly created layout as the Portfolio index page. Now, to avoid any conflict, any NORMAL page that is using the Layout - Portfolio page template MUST be deleted.
If you are wondering if nothing is displayed in your archive layout, you can set the preview by assigning the post type as well just as shown here:
There might be a confusion on your end as to why there is a need to go to Pages > Add New and create the Portfolio page. As you know, the X theme has no Layout Builder and this is where the Layout - Portfolio page template comes in. This is the way to display or create the Portfolio index using the default theme styling. Now, with Pro theme since the Layout Builder is at your disposal, creating a Normal page with the Layout - Portfolio page template is no longer needed. This is the reason why I have mentioned that the page SHOULD be deleted.
If you have still other questions, maybe you can clarify what you want to do with the Portfolio custom post type, how you are going to use it and what information you want to display on it so we can also give a recommendation.
By the way, when you are still building the site, it is highly recommended that you turn OFF any caching and optimizing plugins like Breeze so that you can easily see the site or page changes and not the cache version of the page.
Please check out the portfolio demo now:
https://wordpressmu-1430342-5375343.cloudwaysapps.com/portfolio/
Best Regards.