So I sent Gene the Powerseller an email about the Shadowless set and this is the reply I got.
Unfortunately no one knows the print run numbers, not even WOTC. What’s interesting is that Shadowless and 1st ed have the same amount printed, meaning either the there was only one print run and 1st ed and Shadowless share half that print run OR they had 1 run each.
Another interesting insight is that collectors used to think Shadowless cards were fake compared to the shadowes unlimited and threw them away/destroy them. Since there were Shadowless decks too, they were also played a lot back then. They are indeed rarer than the 1st ed, but not bearing the stamp, they would not mean much for cross-collectors.