Only OUT chests are connected and only on a given surface. So for each planet you need at least 1 IN and OUT chest.
If you build only 1 chest for OUT and 1 for IN, you are always guaranteed a place where the items will be moved. If there are more OUT chests, it is random. BUT it always only applies to a given surface. So you cannot move items outside the planet.
It is not possible to make 1 chest that would increase and decrease at the same time. At least not in the state I have it in now, the entire mod would have to be rewritten and that's not planned :)
Both chests are always needed. One can be put in with a loader, a inserter, or manually. And then taken out into the OUT chest and into the logistics chest (for example)
I can also recommend this mod, which can also change the quality, but is more powerful - https://mods.factorio.com/mod/ic-better-logistic-containers
