In the first Dead Space, to earn the Maxed Out achievement/trophy (for upgrading all weapons and equipment), do you need to fill every possible slot with power nodes, or can you get by with just filling in the ones that actually grant a benefit?
You do not have to fill in all the empty spots to win this achievement. You also will have to do 2 run throughs to be able to collect enough nodes to do this. Everything carries over on your 2nd play through. You can find some guides for the 360 version at least on True Achievements