The only thing that concerned me about your post was that you were talking to the crew as they were sitting on their jumpseats in either preparation for takeoff or landing.
the crew should be performing a "silent" review of safety procedures during that time and should not be either conversing among themselves or with the self loading freight, as it is an unnecessary distraction.
As far as using the term "guys" or "sir or "madam" or the pax name or nothing at all...its all a matter of picking your mark. And that usually only comes with experience. At all time the object should be courtesy and that varies depending on cultures etc...
I note that you say that you have been flying with Low Cost Carriers? perhaps the "norm" is one of familiarity and less formality....