Since vowels are partly defined by the highest point reached by the tongue body, it makes sense to think of the tongue body as the active articulator. For high vowels, the tongue body is narrowing the vocal tract, so it makes sense to ask what passive articulator the narrowing is closest to and what the degree of constriction is. For high front vowels, the tongue body approaches the hard palate. For high back vowels, the tongue body approaches the soft palate.
Glides are vowels masquerading as consonants.