So let me rephrase: if my 24-words are known, would 6 random words as a passphrase on top of my 24-words protect me against a bruteforce attack? I dont need exchange level security because im not rich, but just wondering 
Thanks for the help!
Thanks for the help!
Yes. Your passphrase essentially becomes an extension of your seed phrase. Anyone who has your seed phrase would find an empty wallet, unless they also know your passphrase. Six random words is a pretty safe bet. I'm not sure about Ledger, but Trezor can accommodate 35 characters for a passphrase. That might be the standard for Bip39, so I imagine it's the same with any hardware wallet that supports Bip39 passphrases.