The storage techs are currently bugged; in the next patch they will truly work.
Increasing population increases it, for elves that is building elven residences from settlement.
Next patch full 90 population and the one elven tech to increase storage in settlement will make a resource cap totalling 12,000.
Joseph B. Visscher - JBV3737
Bugs aren't the problem, figuring out how to fix them is.