You are not staking in a specific wallet app (Yoroi), but you are staking the ADA in your wallet to a stake pool, which can be done from a lot of different wallet apps that all control the same wallet.
The access to the wallet are your seed words (keep them safe and secure) or your hardware wallet. The contents of the wallet are on the blockchain (transactions, staking, balance, …).
On Cardano, you always stake whole wallets/accounts. That does not mean that the Ada are sent away. (If someone tells you to send them away to stake, don’t do it!) They always stay in your wallet and you can send and receive totally freely. Every five days a snapshot is taken and ten days later you get rewards based on the balance during that snapshot.
Not with Yoroi. ccvault.io, adalite.io and Nami – other wallet apps – have the concept of accounts. There, you can divide your wallet (same seed phrase/hardware wallet) into multiple accounts that stake to different pools, but then other wallet apps – Yoroi, Daedalus – will only see the first of these accounts.
Other possibility is always to create more than one wallet. If that’s profitable depends on the amount of Ada. Below several thousand Ada, I would not want the hassle of staking to more than one pool.