Folders vs Collections - related to the case
CMS it’s better for one template for X pages (blog and also portfolio page) and really easy to add/edit/remove items + create pagelist
Folders is a way to organize your site hierarchy (Great for SEO for example)
conditional-visibility
If you have 6 portfolio pages and 3 of the 6 are little diff you could add a conditional-visibility (Show section X only if statement Y is true/false).
Another option is to create two collection (collection for "uix works " & “after effects works”).
Last is regular pages & duplicate page/items (Option 1 & 2 a lot more dynamic).
next/prev
About next/prev - only manually for now:
By CMS (create custom field “next link” : and put url inside)
By pages inside folders manually add URL to the button.