They could be yelling because they are in a competition or trying to get someone's attention. Sometimes, it's just a way for them to express their emotions freely.
The bellhop could have been yelling because he was caught up in the intense and confusing situation, trying to make sense of it or get someone's attention.
Armin could be the storyteller. Sometimes characters take on this role to provide a unique viewpoint or to drive the narrative in a particular direction. But we need to know more about the story to confirm it for sure.
Armin is still alive in the manga. The story developments don't result in his demise. His presence remains significant and continues to shape the narrative.