Since the spell description doesn't otherwise say, I'd let each globe give off as much light as a lantern would, or I would allow the caster to dim it to only illuminate a 5ft area.
The other day an issue with Dancing Lights the cantrip came up. The spell was being used as "one faintly glowing, vaguely humanoid shape". Does this option give off the same amount of light as the torch or lantern version? How much light does the will-o-wisp version give off?