An LLM running one query at a time can already generate a huge amount of text in a few hours, and drain your bank account too.
A "different agent" is just different context supplied in the query to the LLM. There is nothing more than that. Maybe some of them use a different model, but again, this is just a setting in OpenRouter or whatever.
Agent parallelism just doesn't seem necessary and makes everything harder. Not an expert though, tell me where I'm wrong.