“A ‘giant’ in Biblical times could have been someone 6 feet tall.....”
Yep. People can read into passages like that all sorts of things.
Regarding “The Nephilim were the offspring of heavenly beings who were placed in the spiritual realm to watch over the earth in those days. They were principalities in the heavenly realm”
That sounds like spiritual entities but we really don’t know what they are. Jesus did not elaborate.
Did He mention them at all?!
Because what you've written suggests that Scripture records Jesus of at least mentioning them.
Chapter and verse?
Regards,
Jewish explanations interpret them as hybrid sons of fallen angels.