So... I figured out the exact spots for the spawns 👍 The primary spot is just behind the red obelisk on the thin little strip of land near the southern island. (I almost always see one spawn there) I also find them frequently spawning around the “back spike” of the red obelisk. You will almost always find a quetz around these two places. (At least on mobile) If you want a high level, just kill the one that spawns at these two places and a new one will always respawn back at those two places. This technique worked for me.
I do the grapple to your argy Methed then it falls by giga so I kill the giga like I always do with spinos and rexes beacause it’s easy with flying mount but this dude had lots of health so the quetzal woke up before I finished the fight