I Want to Use POP Custom, Which Recommendations Should I Follow First?

If you are using the Compare Data sub-tab, the recommended approach is to complete increases before making decreases.

Decreasing optimization elements is generally most appropriate for older pages that are stuck. It is a higher-risk, higher-reward strategy, so first make the recommended increases and see how the page responds.

Also check the strategy POP is recommending and make sure you are not following a different strategy by mistake.

If you are unsure which path to take, follow the Content Brief. It is designed to make the more difficult SEO judgment calls for you and reduce guesswork.