One of the biggest motivations for Taproot was that Schnorr signatures/public keys can be combined into a single signature, and be indistinguishable from a singlesig.

MuSig2 is one signature aggregation scheme for Schnorr signatures, and this is the one whose implementation BIP 327 talks about.

It's a big win for both fee reduction and privacy. If wallets implement this scheme, then a 2-of-2 or a 100-of-100 (or any n-of-n as far as I can tell) will be as cheap and indistinguishable from a regular singlesig Taproot spend, which also means greater anonymity for all Taproot wallets (is it a singlesig address, is it a multisig address, is it a multisig with alternate spending conditions like Lightning, who knows!)

MuSig2 support is also planned for Lightning (along with Taproot), so in the case of a cooperative close, your LN channel close will look just like a Taproot spend (with lowered fees as well).

Also, MuSig2 will make LN channel gossip messages smaller. From what I remember, when information about channels is being passed around the network, it includes proof that the on-chain UTXO belongs to this node by providing signatures for 4 keys (2 Node ID keys, and 2 UTXO spending keys). With MuSig2, you could have a single signature for all 4 keys, leading to lower bandwidth usage.