Effusiveness is the name for that quality — how much someone pours out their good feelings. You can like a person’s effusiveness (it makes a room feel welcome) and still notice that a shy guest might freeze under it. Same idea as effusive, but as a thing a person has or shows, not a word that sits in front of “thanks” or “smile.” It is rather a formal, bookish noun; in speech people more often say “she is so forthcoming” or “he lays the praise on thick.”

熱情洋溢、溢於言表