However, it appears multisig creates 3 mnemonic/seed phrases anyway, so multisig seems to provide the mnemonic/seed phrase storage protection as well as payment protections.
Versus... SSSS which is specifically for mnemonic/seed phrase storage.
That's right, but take note that spending MultiSig is a more expensive than single Sig.
Depending on the number of required signatures and script type, the transaction's input size alone can reach more than a minimum of 100vB per input spent.
e.g.: Include the rest of the transaction's data and it'll be about 190vB for a "
1input-2outputs" 2-of-3 P2WSH MultiSig spend.
That's not much with a low 'fee rate' of 1sat/vB but the difference will be night and day when you have to use 10sat/vB and spending two or more inputs.
e.g.: About 500vB for a "
4inputs-2outputs" 2-of-3 P2WSH MultiSig spend, that's a total of 0.00005BTC fee for 10sat/vB fee rate.
So, you should consider that when deciding on your wallet's setup.
One deciding factor is how often you send to your wallet:
- Frequent inbound transactions with smaller amount is worse for MultiSig setup because it'll produce more UTXO to spend as input
and your outbound transactions would use more inputs to cover the recipient's amount.
(This is applicable to any regular wallet but MultiSig's size is higher so the impact will be worse) - But if you're planning not to send too often, and send in higher amounts instead (accumulate more before sending to the wallet), fees will be smaller when spending.
(still higher than single signature of same number of inputs though)