I'm currently playing the mobile version of the game, so I don't know how applicable my knowledge might be to your version.
That said, I believe that the encounters that you seem to be describing--fur-traders, wandering armourers, etc.--are random occurrences. They're primarily found on roads (even if those roads are barely such), with the road between Rhoneis and Nivarian being guaranteed to have one or two encounters on each new visit (i.e. each resetting of the area). Which you get (and outside of that one road, whether you get any) is, as mentioned, determined randomly.
So--in the mobile version, at least; I don't know whether it works in the PC version--if you're looking for a particular encounter, you could perhaps reset a given map until you get the encounter that you want. To do this sit in a neighbouring map, just outside the entrance to the desired map, then save. Now whenever you reload that save, the desired map should be reloaded, allowing you to reset its contents, and thus its random encounters, multiple times.
That said, I haven't found much advantage from the travelling -armourers or -alchemists, myself. But then, it's very possible that I'm forgetting how their stocks compared at low levels.
(I do think that the fur-traders are very useful, however.)
