I found this queen cup explanation from Canadian Beekeepers in Facebook enlightening:
Quick Queen Cell Guide..
Queen cups (play cups) - common spring/summer
Charged Queen Cells - very high risk of imminent swarming
Sealed Queen Cells - probably already swarmed
Opened Queen Cells new virgin queen likely
Elongated - larvae fallen from royal jelly, often duds
Swarm cells, supersedure cells and emergency cell will vary in number, location and sometimes season