Decide your use: quick melt (sandwich) or longer bake (gratin/loaf), then choose the substitute that matches that melt behavior.
Swap using the listed ratio: for direct melt recipes, use 1:1; for sharper cheeses, use the reduced ratio.
For best texture, shred sliced cheeses and spread evenly so they melt in a thin layer instead of clumping.
If the substitute tastes too sharp or salty, mix it with one neutral option (like mozzarella) before adding to the dish.
If the substitute seems too firm, bake/heat a bit longer or cover the pan to trap moisture and improve melt.