I know for PIP you can select and move the PIP window to the four corners in 3.7.
As for Guide and My Show windows... the preview window may be on either right or left sides depending on the specific menu screen but for the program guide it is on the upper left I believe. Those can't be changed using the GUI as I under stand it.
I would LOVE if a preview window could be inserted in places were it currently isn't (but could be) just because they didn't "enable" or make room for it. The search menu comes to mind. Limited Searches can be done with a preview window (partially obscured by the "search" window)... Preview audio can be heard while doing full searches but no PIP (or can you? I haven't tried keeping a PIP open in "search mode" recently).