For the best crunchy, airy texture, use well aged, low moisture cheeses and avoid very soft or high moisture varieties. Freshly shredded cheese usually melts and crisps more evenly than pre-shredded cheese, which can be coated in anti-caking agents. If your oven runs hot, bake on the middle rack and start checking early so the cheese puffs turn golden and crisp without burning. Batch size will affect spread, so if you prefer smaller, more popcorn like bites, scoop slightly smaller mounds and reduce the baking time by a couple of minutes while watching closely.