I started using geo nodes recently and sometimes the "Group input - geometry" is so far away and there are so many overlapping connections... I don't know if doing that makes any noticeable difference in performance. Does anybody know if this is memory wise inefficient (like if Blender has to now individually process the geometry the same number of times as the number of node copies or if all just a light referencing or something like that)? Thanks!
As far as I know, it makes no difference at all. It behaves like in a program where you access global variables. No matter how many times you do that, the values always stay in memory once, no matter how many times you access them.
For each additional Group Input node a very small amount of memory is used in the node editor -- to remember the position of the "Group Input"'s node displayed in the editor and which of the outputs of a specific instance are actually attached. The amount of data is small and even a dozen group input nodes won't add much extra memory.
Is that extra memory wasted? Not if it makes your node groups easier for you to read.