So, the caches can be in any random location in between? like, for the first one, any universe between -5,-5 and 5,5? location's static or totally random?
They are located in a galaxy on or between those coordinates yes. for 5,5 to -5,-5 it would be located in 1 of 121 galaxies in that 11x11 square. It's location is the same for everyone.