Q: What does it mean if two editors have been assigned for my paper?

I understand that you are quite anxious about the submision of your paper to your target journal. However, there is nothing you need to worry about. It is true that a journal editor or editor-in-chief (EiC) is responsible for making all major manuscript related decisions. But in some cases, journals have Associate Editors, Assitant Editors, or Section Editors to help the EiC manage large submission volumes and make important decisions. So in this case, the Assistant Editor initially screened your paper and forwarded it to the EiC for consideration. And the editor decided that your paper was worthy of being considered for a peer review (hence the Under Review status). So everything is fine and your paper is being peer reviewed.