[@Unknown100]
Basically only the scientists know about supernaturals. So the inventions they make come from them. 
Which means no one knows about angels or demons except for scientists.
For this purpose God would not be involved. Angels can say God exists but no one can play that being nor can they involve them in anyway other then explaining where they came from.

Edit: though for angels and demons I would prefer some form of they appeared suddenly or some other creative explanation...then add the rest of their history over a god explanation.