Presently, PSG4 does global changes for slide timing and transition timing. However, a global change for things like scaling (e.g., 'fit to frame') and font options (e.g., font type, font size, BOLD, etc) would be very handy, particularly for shows with 150-200 slides.
ProShow Gold 4 already has the capability to globally change the font options you mentioned. In the Slide Options window just right click on the font name, size etc. and you will see the choice to copy to all slides, selected slides or all captions on that slide.