For example, let's say you have a 5 page website and each page has a different content setup, maybe a different layout.
It really depends on what is the difference between them.
Often you can use the same template and switch parts of them (which you have in chunks) by a listbox-TV: box A==[[$box_a]]||box B==[[$box_b]]||box C==[[$box_c]]
or you can use MIGX to have the option for adding multiple boxes(chunks) and move them by drag/drop into the correct position.
If you have 'functional pages' with no content but different functions (like a contact-page, galleries, news-listings) and same layouts you can put your snippet-tags into the content.
Tip: disable richtext for pages like that before putting snippet-tags into it.
If you need additional CSS/js on some pages there are also multiple ways to add them dynamically.
There are for example these (seems undocumented) output-filters:
'cssToHead' 'htmlToHead' 'htmlToBottom' 'jsToHead' 'jsToBottom'
which can of course also be used in combination with a MIGX-TV for example.
If you need completely different TV-sets in the manager you can use static-templates which point to the same template-file but have different TVs assigned to them.