These are Yunho and Mingi (jean jackets) and San and Wooyoung (in red and black) covering BTS, NCT, & Wanna One's dances. They are amazing!
Note: Before debut they were known as KQ Fellaz (or KQ Boys.)
Watch Ateez's debut and predebut stuff here:
KQ Fellaz-Yunho Solo Performance Video
Ateez Debut (Treasure & Pirate King)