Ripple is a global payment protocol aimed to provide fast transactions and cheap payments internationally. The network uses a digital currency known as XRP (sometimes it's referred to as Ripple). Unlike other cryptocurrencies Ripple is not aimed to replace banks, rather this project is created to improve the work of banks (including transactions between different banks) via blockchain solutions.
Nexus (NXS) coin is available on a few exchanges, including Binance. You can purchase NXS for BTC. This coin can be staked or mined and serves as the core cryptocurrency of the decentralized Nexus network.
Tezos is a smart contract platform with its own blockchain and a native token (Tezos, XTZ). The governance is performed via Proof-of-Stake algorithm. It means that stakeholders (those who own at least 10,000 XTZ) vote for changes in the protocol. These validators ("bakers") get rewards for the performance of validation. The rewards are generated via inflation. Those who delegate their XTZ to bakers can earn, too.
Tezos has a built-in "self-amendment" mechanism which makes it possible to shape the network without having to make forks. It keeps the community united and makes development process easier.