It is possible to add entrys into a Section's body like images, cards, etc. You can even add a section to it's own body, don't do this. Our server will try to recursively build it and fail so you won't be able to push any updates to the site until you remove self-references within modules.
Although you can embed things into sections, currently not able to. So it won't break to add a Profile inside a Section but it won't do anything either except make pagees load slower.
Should I center cards on the page if they are not part of a groupd module? (see /modules-example-page/)
According to my /how-to-break-things page it is totally fine to add "featured" cards to a module container, it will revert from featured stylign to normal card automatically (why? idk but that's what happens as far as I can tell. It's ideal behaviour with unknown causes.)