Spool V1 exclusively supported "stable assets" as deposit currencies. To ensure ultimate stability, the Spool DAO opted for supporting 3 "stable assets" in particular, namely: DAI, USDC, and USDT.
Spool V2 adds native support for both Volatile Assets as well as "Multi-Assets". Volatile Assets are easy to understand: Any token meeting the basic token standards will be supported, examples include, but are not limited to: ETH, CRV, and GMX.
Multi-Asset Vaults refer to the support for assets existing out of underlying assets. The easiest example would be "ETH/USDC" Liquidity. Multi-Asset Vaults would allow a Vault Creator to create a Smart Vault which rebalances ETH/USDC liquidity between multiple decentralized exchanges.