The NXT Client is the official NXT wallet. It's a full node wallet with all the features that the NXT Platform has to offer, inlcuding asset issuance, trasfer, exchange, and more. Users can also enjoy advance monetary features like multi-sig addresses, phased transactions, and coin mixing. The NXT Client can be customized with plguins, such as the decentralized escrow, Quack.
Ardor Tokens can be currently stored in the NXT Client as they are assets on the NXT blockchain, until the Ardor Platform is complete.