My personal opinion is that there aren't any hard-and-fast rules about any of these experiences. Entities come in many different forms etc. I guess a 'godhead' experience could be categorized as any transcendental experience where one feels the presence of the source....whatever that means:surprised 

I know what I consider a godhead experience, but I feel that it is a very subjective experience so I won't bore anyone with the details. However you want to label it...I think ones knows when one has it:?