Nice to see a detailed breakdown like this. Loading time is surely a part of CX, as the less frustration and wait the better the overall experience.

I for one always remove the exif’s and other data from images — imageOptim and imageAlpha work best (for JPG’s and PNG’s accordingly) resulting in much smaller file sizes.

For diagrams / illustrations etc PNG is usually better (especially if it can also be color-reduced without quality loss) and JPG for photos.