you can use Procreate drawings as background images, best through the universal clipboard: in this case you would do all vector editing inside glyphs on the Mac
if you have a way to produce actual vectors, you should be able to paste them as well; though we may need to adapt the clipboard handling inside Glyphs.app (let us know)
and there are solutions like AstroPad, which turns the iPad into a Mac input device, and you could use your iPad pen with the Glyphs pencil tool: the vectors may need a lot of cleaning up afterwards
I am very unfamiliar with how the software works (Glyphs). There is a lot to learn about the latter.
I can use Adobe Illustrator as I come from a graphic design background. Maybe I can draw them on Procreate, one letter after the other, then export them to illustrator, vectorize and eventually import them to Glyphs? Does that make sense?