Hi Fred,
Generally speaking, yes, you’re right. Processing results from Emlid Studio are in the POS format, which belongs to RTKLib. So at the moment, you can convert it to GPX/KML with the RTKPost only.
However, why don’t you try the Geotagging feature in Emlid Studio? All you need is _events.pos file and folder with photos. So the conversion to GPX is simply not needed.