Would users in this case have any other security enhancement use cases by using the revealer?
Considering its price, I would say the main attractiveness is how cool the concept is. If you put it securely and someone who knows that you own Bitcoin is trying to rob you, they would probably be finding a paper with words on it rather than a paper that looks like an useless printed piece of paper.
2) If I have multiple seeds / wallets then do I need to order multiples of these or can multiple of them be printed / stored on one PVC sheet?
You can use the same secret key for all of them. You aren't supposed to put all of them together. However, you do need to use the corresponding PVC sheet with the noise on the corresponding printed