The Marines separate males and females into different companies in boot. Also all females go to Paris Island. Where as males from the western half of the US go to MCRD San Diego. In Marine boot we weren't allowed to smile. Smiling would get you yelled at. And yes you do need to practice your stone face and thousand yard stare.
At least for Marines. Against can't speak for army. Also I wouldn't worry about the crucible or anything similar the army may have. For me (and most of my platoon) the crucible was the best part of boot.
Again, wouldn't worry about the food thing. After a couple of weeks you'll learn to eat fast.
For the most part boot camp kinda sucks, but isn't actually hard. I know when my recruiter told me it would be 90% mental and 10% physical inside my head I laughed. I figured the mental part can't be too hard, and the physical is what I need to prepare for. Trust me it's the other way around. The mental part is the part that sucks. Physical... I mean the hikes were kinda hard. But otherwise it's all pretty easy.