Objectivism vs. 'Pragmatic Existentialism'

I'm interested in finding out what the key practical differences are between Objectivism and what I will call 'Pragmatic Existentialism' for lack of a better term.

I ask because from time to time I come into contact with folks who are Objectivists and they seem to have the same interest and commitment to personal integrity driven by morality and happiness that I do.... I often even use the same nomenclature (like "being selfish isn't immoral, it's about honoring one's commitment to personal integrity") and I recently listened to all of Leonard Peikoff's podcasts and with few exceptions (mostly about politics which don't interest me much) I was pretty much in line with everything he said.

The one distinction I do see different is that I, who always called myself an existentialist, assert that everything is perceived so even a statement like "reality exists outside our perception" was brought into existence as a perception.

But that doesn't seem to have any bearing on the fact that we exist as individuals and therefore 'for' ourselves, and therefore have a moral obligation to create an environment which both maximizes our opportunity and safety and therefore have a obligation to pursue unrelenting integrity in our personal values. (The philosopher I most identify with would be Sartre...even though I've only read others explain him...I've not read any philosophy books or Rand...I've just been thinking about this stuff since age 11 when I concluded there was no evidence of god and refused to get a Barmitzvah.)

So, back to the point, I don't really understand what makes one Objectivist vs. someone like myself who is just a critically introspective person.