Do you have some advice on how to evoke feeling of harshness in the setting without making it caricaturally grim or simply stingy with resources? Something like tolkienesque First Era Beleriand with inaccessible gods and great danger nearby but with less superpowered elves and less focus on nobility?
It seems fine. I guess the light load/easy terrain speed is a strain depending also on how you interpret "easy terrain". I can imagine doing it on a well maintained road.
Also choosing to go light/easy looks like a statement from a player "We gotta make it on time". It deserves extra speed. And without load of food/water/tent they need to do it in friendly and inhabited areas.