Decide your use case: topping/crumb vs. melting for baking; this determines whether you prioritize crumbliness or melt.
Choose the substitute from the list that matches that use case first, then apply the listed ratio.
If the substitute is saltier/tangier than caerphilly (e.g., feta), use a reduced ratio and taste after baking or heating.
For better texture, shred harder cheeses and crumble crumbly cheeses; mix into the base rather than dumping on top for more even behavior.
If your dish needs a softer bite, warm the cheese with a spoon of hot dairy (milk/cream) for 30–60 seconds before stirring in.