I'm a bit confused about what exactly to group to optimize my site.

My understanding is that anything that is grouped will be converted to an image.

So I probably don't want to group text objects since that would be bad for SEO content and probably have other bad side effects.

If I want my graphics to popup I suppose they shouldn't be grouped. However, if I don't want them to pop would it be a good idea to group them?

Am I leaving anything important out of this?