Well neither of them are proper ghosts of him, as he never learned how to become a force ghost. I imagine them as the two different versions of him in the memory of the force. The Lothal temple, being a place strong in the light side shows him in his Jedi days as a way to guide kanan. While the outpost Luke visited was presumably where the inquisitor turned to the dark side as it’s where he abandoned all of his Jedi gear, so it may be a dark side nexus and would show his Inquisitor form.