Can espers in Mob Psycho 100 create any kind of superhero powers or are there things that are known that they can't do? I believe that really depends on the esper himself/herself. This lists all known psychic abilities that espers can possess. If one is creative enough, then an esper can, hypothetically, create his/her own moves and techniques that are unique, based on how he/she applies the known techniques they can do. So, yes, I believe it's possible they can create or replicate techniques similar to superheroes (I am assuming you are referring to comic superheroes like those in DC and Marvel).
As to what they can't do, I cannot recall this ever brought up in the anime but in Volume 10 Chapter 78, it was noted that espers have difficulty performing two simultaneous actions at once, albeit it is not impossible.