Maybe is used if there is no way to figure something out without trying it (example "maybe it will be faster to use the back staircase") perhaps isnt something i see in modern use very often but it can be used when you think you know how to do something and in books and movies often has an ominous tone to it (which might be why i haven't seen in very often in modern writing…) probably is for when somethin is more likely to happen then to not happen