PlexCard Visa : Would it be legal all around the world?
VISA and MasterCard cards are issued by banks all over the world, that have a valid license. It's not the first time we see cryptocurrency based VISA card. Those cards can be used in every shop (online or physical) that accepts VISA cards.

If this PlexCard VISA card is issued by a bank that has a valid license to issue VISA cards, then the card will be legally accepted wherever VISA cards are accepted.

As for the second question (fast transaction confirmation time), I don't know about PlexCoin but there are other coins with near instant confirmation times, that are using techniques like faster block time and/or MasterNodes.