The stew meat is what makes this so quick and easy to make. You can use a better cut of meat if you want but then you'll have to slice it up which I think just makes it more of a pain with extra steps, time and clean up but if you want to go that route have at it.
You can use either sesame or toasted sesame oil for this. Whichevs is easiest to find or skip it entirely if you don't have any laying around.
Take it ease w/ the corn starch. You're gonna be all, it didn't thicken up and then like 15-20 minutes later it will so if you keep adding more from the jump you're gonna end up w/ sludgy ass beef & broc.