We now have suzanne in the forum lending a helping hand with music theory. Let's step forward and supplement that with information for those seeking it. Can you contribute, even if only asking questions?
Andy, I thought we could start the CAGED discussion from scratch. I just started a new job (after several months of unemployment) and yes I am an engineer. Not working is great for guitar playing, but not for the wallet. Anyway I will get together some info on intervals and post it also some on the CAGED system.
As to why minor pentatonic over G major because it is easier (less notes) and it is used a lot in blues and rock. If you prefer the G major that is fine. Either pattern can be moved anywhere on the neck for different keys. Next question, the 3rd and 6th are always minor in a major key. For example, all major scales have the chord pattern as follows: I, ii, iii, IV, V, vi, viidim. Where capitals are major and lower case are minor. We can explore more of why this is so if you'd like.