Terms for addicts are easily enough improvised by adding -oholic to the name for a specific social media platform, e.g. “Twitter-oholic,” but is there something more generic, & less unwieldy & artificial than “social-media-oholic”?
Terms for abstainers seem even harder to come by.
The very term “social media” seems to me to provoke the question: “How could any communications medium not be social?”
The M-W definition for “social media” would appear applicable to EL&U itself, so although I am a total abstainer from Facebook & Twitter & even smart phones, one of the addict terms may apply to me, though the recipe above would generate a pretty unwieldy result.