On the hypothesis that Paul is communicating that the “appearance” of Jesus here was purely intra-mental, it seems probable that the experience was a supernatural vision from God (the normal way God communicates something like this intra-mentally).
This is relevant because this language of “revealed his Son in me” etc. does not recommend a visual component at all, and so does not really accommodate the vision theory. So, by modus tollens, Paul is not communicating that the appearance of Jesus here was internal.
Paul decisively rejects the view that Jesus’ appearing to him was vision-like or purely internal to his mind.
This is relevant because, if Paul then goes on to describe an internal experience associated with Jesus’s appearing, we can safely conclude that it is only focusing on the internal part without excluding the existence of an external part. (And truly, we can anticipate that a physical appearance of Jesus would have both an internal revelatory aspect, and vivid external aspect, even if one is described without mention of the other.)