Diffusing definitely gives you more curls than air-drying would. And if you're using the right products, your curls would even stay all day. Mine used to get a bit looser throughout the day. My suggestions is, thought, that if you have to diffuse your hair and get curlier hair than you want, just run through your hair with a leave-in conditioner. That way you're not pulling on your hair too much, it is easier to rake through with your fingers, and you'll be pulling down your curls a bit to create nice waves.
2b/c, fine, low-med porosity
Co-Wash: Live Clean Fresh Water Conditioner
Leave-In: Yes To Carrots Leave-in Conditioner
Styler: Herbal Essences Totally Twisted Curl Boosting Mousse, FSG, GF Pure Clean Gel