Wasn't aware of how the passphrase thing works on Trezor devices : basically is like adding another word to the seed and therefore creating a new wallet?
Exactly. With the passphrase, new keys and addresses are generated
Anyway considering recent ledger mess up, even if it's a bit offtopic, would you be so kind to share what you consider being better solutions?
For bitcoin, wallets on airgapped devicen is better. If not spending the coin for a long time, you can use a paper wallet too. But wallet on airgapped devices, you can have a watch-only wallet too which is optional but can make broadcasting transaction easy.