There are many different methods to reading tarot cards, just like there are many different opinions and attitudes toward intuition, spirituality and "psychic" work in general.
I like the more modern, no drama, holistic approach. As I see it, any given card has multiple aspects, both positive and negative meanings that are all part of the same card...just like the positive and negative terminals are inseparable parts of the same battery, or the north and south poles are inseparable parts of the same magnet. The card, the reader, and the person getting the reading are all part of the same wholeness of the cosmos...that's the connectivity that allows a reading to be meaningful and useful in the first place. In that frame of reference, which way a card is oriented on the table is relatively unimportant. Often I'll use that contrast of upside down vs right side up cards as a nudge toward one meaning or another, or a gentle spin on the overall pattern in the cards, but not so much as to make a complete change in the card's meaning.
