Note on Socrates - He would argue that a sophist is a "Debater for hire" whereas a philosopher has a passion for/vested interest in truth.
Most of what we know of Socrates comes from Plato's writings. But to what extent do his writings give us the historical Socrates vs. a literary character?
One of the theories is that the early writings of Plato are more historical. As Plato grows and matures through his writing, we begin to see a more literary Socrates.
Here is the problem - How do you know what works are earlier, and which are later? We get that from the picture of Socrates we get. So really, we don't know - it is a subjective analysis.
Plato takes the best of Heraclitus and the best of Parmenides and arrives at a grand synthesis.
Much of Plato's work is to bring these very disparate ideas together. He was enormously influenced by those who have gone before him.
The ancient perspective is that your metaphysics were fundamental to understand before you start to investigate your epistemology.
Before you can properly discuss what we know and how we know it, you must first understand what reality is like.
For the moderns (Descartes onward), this is opposite. You would only do metaphysics after you have your epistemology down.
The Post-moderns would agree that the epistemology is fundamental, and that metaphysics comes from that, but they challenge our actual ability to do either.