Originally posted by GhostOokami:

Scenario, I'm trying to place 1 wall on top of the other, my cursor has to be perfectly on the top few pixels of the first wall or the snap point just goes wherever it pleases. The is even worse when I'm trying to build something in front of me while I'm trailing behind, like a platform in the air or above water

Scaffolding. Build stairs and platforms to give yourself better vantage points.
In the first scenario you illustrate, for example, the solution is to build some stairs to give yourself a higher vantage point to place the piece.
Building above water? Build yourself a raft so you can "stand" on water. And so on.