I’m not an expert on Philadelphia proper since I live out in the suburbs… but I guarantee you don’t need to go to Pat’s or Geno’s. If you do, at least Geno’s new ownership isn’t openly shitty.
Basically, it doesn’t have to be gourmet (but it’s fine if it is), it’s junk food. I’m happy with sauteed onions, mushrooms, cheese whiz, provolone, beef, chicken, whatever.
My favorite spot near me does cheese whiz + steak + crumbled bacon. Also good: provolone + steak on motherfucking garlic bread.
But yeah, any place that will give you takeout wrapped in foil is probably fine. Or if you find some place that does really nice sandwiches that’s fine in a different way.