Think of your pages as a funnel with 3 layers.

On the top of the funnel
(blog posts,infographics,content assets)
– these pages usually get the bulk of your backlinks because people link to content.

Middle of the funnel would be your product demos, product comparison pages, case studies.
– not the most attractive pages for links since they’re more geared toward your products.

Then bottom of the funnel – service/product pages.

Your links should flow downward, because the 2 lower levels don’t attract as much links as the top layer. It also helps with the customer journey as you aim to take them from being a visitor to a customer.

Only link out to case studies if it helps convert your Bottom of the funnel visitors into customers.

That’s how I would approach this.

Hope it helps!