Well, yes, in a way. The GPS will store it in its own format when you upload, then TF will store is as GPX when you download.
GPSU route might work, too.
Datum shouldn't be a problem. It doesn't matter what datum your GPS is set to -- it is always sent to the computer (topo!, TF, GPSU) in WGS 84.
Of course any file could be saved as another datum, but GPX files are always WGS 84.