That speakers differ by how talkative they are is well known but rarely taken into consideration by professional (socio)linguists. In that connection, a useful word is ‘garrulous’, defined in the OED Online as follows:

“Given to much talking; fond of indulging in talk or chatter; loquacious, talkative.
“Of speech or talk: Characterized by garrulity; full of long rambling statements, wordy.”

Apropos, ‘loquacious’ is also useful, except that ‘garrulous’ is more appropriate when describing a person pejoratively, i. e.,  as being overly talkative.