Taproot is a big upgrade, in P2SH and P2WSH multisig transactions, the higher the numbers of keys used to generate the wallet, the higher will be the transaction fee, but with Schnorr signature, the keys are aggregated into one single valid key and produce a signature which will be used for the on-chain transaction. This makes Taproot transactions to be like a single wallet with 1 Pubkey transaction with low and same fee irrespective of the number of keys used to generate the wallet. For example, 2-of-2 multisig fee will be the same paid by 15-of-15 multisig fee.
The transaction is indistinguishable and look like single pubkey wallet in which a blockchain observer can not even know if the transaction is multisig or not. It also create a recovery option in which an alternative means will exist for recovery, like in 3-of-5 multisig, if one key is lost, their is an option to recover your coins as there are still other 4 keys in which 3 is needed to provide signature.
It will also benefit the lightning network, two people that partnered together to use lightning payment, they can both join their signature together to produce single valid one, which makes both parties to be able to sign with individual signature and makes closing of a lightning channel to look like that of normal payment. With Adaptor Signatures, atomic swap will be possible which can not be differentiated from normal Bitcoin transaction.
You can watch this YouTube video to know more about how Taproot upgrade will help in scaling, efficiency and privacy.
https://youtu.be/1gRCVLgkyAEThese links will be of help:
https://github.com/bitcoin/bips/blob/master/bip-0340.mediawikihttps://github.com/bitcoin/bips/blob/master/bip-0341.mediawikihttps://github.com/bitcoin/bips/blob/master/bip-0342.mediawikihttps://medium.com/interdax/how-will-schnorr-signatures-benefit-bitcoin-b4482cf85d40https://medium.com/interdax/what-is-taproot-and-how-will-it-benefit-bitcoin-5c8944eed8dahttps://medium.com/digitalassetresearch/schnorr-signatures-the-inevitability-of-privacy-in-bitcoin-b2f45a1f7287https://bitcoincore.org/en/2017/03/23/schnorr-signature-aggregation/