F variants are imported from Europe mostly, but sometimes from places like Singapore and Malaysia and oddly Russia too. My cousins G920F Galaxy S6 has the box written all in Russian and the instruction booklets as well are all in Russian.
W8 are Canadian variants, a good choice for someone who's on a tight budget, can easily flash the generic Canadian ROM, get rid of carrier bloat (if any), have decently quick updates and more importantly, good LTE band support.
Most of those phones come without their original boxes, but even the ones that do get the boxes dumped (or re-packed) and the accessories kept for the shopkeeper himself, whereas the phone is sold with so-called original accessories (and usually no box), which are actually fake, you can tell by the quality and the font of the text printed on the chargers and the fact that they make a weird squealing noise when connected to a wall socket.