There's been a lot of discussion in the community about the penalties of changing themes, and also of modifying themes.
Is it true that if you create a layout with one theme and later change it, the original theme information is still embedded with the file and cannot be safely deleted?
Is it true that if you modify a theme on a layout, that modification adds 'weight'?
Is it true that if you modify a theme and then un-do the modification, the mod is still embedded? If so, is that not the case if you use the 'Apply Themes...' button on the Appearance Inspector Tab? Or does that button just make one more mod?
How costly are these various changes? Are they worth worrying about, or so trivial that we can ignore them?
Other than the above, and the obvious requirement to move some objects around, what are the downsides of changing a Classic theme to any other theme?