For me 'very light' would be an Olympus XA and nothing else. Over the years I've perfected travelling with hardly anything, a small shoulder bag is normally my limit. Alas, those days are over for a while as we've got a small baby and now carry more stuff to the shops than I used to take on 4 week holidays!
Years ago I did inter-rail around the Continent and took an F3 with the 16mm fisheye - if I did it now I'd probably choose a 24mm lens. Back then getting film was easier than now, so taking stock with you is essential - the weight of film soon adds up as does it's physical space. Maybe one of these would help:
In any event, one camera, one lens will lighten the load, mean less to worry about and challenge you to find interesting compositions.