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You should read our article comparing 2-of-3 multisig with 3-of-5 multisig, which goes deeper on all the questions and scenarios you're asking about: https://unchained.com/blog/bitcoin-multisig-2-of-3-vs-3-of-5/
but to briefly answer your questions: you need to secure 6 elements for standard 2-of-3 because we assume you should always have a hardware wallet and a seed phrase backup.
the 4 items you could lose are: 3 hardware wallets and 1 seed phrase. That would leave you with 2 seed phrases.
I was confused about securing 6 elements for the 2 of 3 multisig, as a seed phrase is also a key. The link you send me make more sense to me. Thanks.