@ricmac, can’t speak for the community but here’s how I do it:
1. Optimize every image losslessly, regardless where it’s used. Using ImageOptim with aggressive settings for manual, and Imagemin Guard for automated optimization.
2. Make special optimizations for key images (logos, icons, those getting accessed a lot). This is a manual process where I play with different formats, use different tools, &c. (and compress, too, sure).
Reliable process that allows me to stay close to the output.