You cannot not look at the top 5 cards of your deck to know how many AtomSIGNI will be revealed by this ARTS's ability, before revealing them to your opponent.
Therefore, you can only declare which of your opponent's SIGNI to be freeze and downed, and banished after this ARTS is resolving.
Your opponent does not need to know the order of the cards you returned to the bottom of your deck.
If 4 AtomSIGNI are revealed by this ARTS's ability, the card that is drawn is the first card revealed by this ARTS's ability.
At the time you begin to resolve Fortune Five's ability, the revealed cards are still within the deck. Because the revealed cards have yet to be returned to your deck by Fortune Five, the revealed cards are still "at the top of your deck."