Is a push-up/pull-up superset workout effective for muscle building?
Yes, and as you grow stronger, you will need to add a weighted vest or a belt that holds weight. Eventually, you’ll be doing like 50 pushups, and the reps will be more for endurance rather than building muscle. I would say once you can do 50 pushups, I would start adding weight to make it hard to achieve 20 pushups.
Is this more effective than doing 5 sets of Pushups followed by 5 sets of Pull-ups?
Yes. For reasons you probably guess, it saves time and is the most efficient use of energy.
They’re better than nothing.
Push-ups are too hard for weak people and too easy for strong people.
Pull-ups and chin-ups are hard for weak people (but can be assisted with bands) and easy for strong people (but can easily be weighted). Neither is true for push-ups.
I prescribe chin-ups for most trainees and bench press and press instead of push-ups. Also squats and deadlifts of course.