I don’t think we will ever be able to know about the proportion of mounted Goths, Vandals etc, it is much debated.
Sarmatians and Huns, though, I would think would almost all be mounted, especially the latter, who weren’t short a bob or two. Both of these races were famous amongst the Romans for always riding. Some once “proved” that the Huns couldn’t all have have been mounted by calculating the available pasturage in Hungary, but I’ve read arguments against that.
I’ve played some of Simon MacDowall’s Comitatus games and there are a lot of cavalry about, and dense masses of German and gothic foot.