--snip--
I have also read 2 things that seem contradicting. There is a popular scam where they sell used hw wallets after they have copied the seed phrase so they can recover it later when the new owner puts money into it. That's why they officially warn to never buy second hand hw wallets. But I've also read you can create new seed phrase and private keys.
--snip--
I just wanted to elaborate on Charles-Tim's answer a bit.
The problem here is dual, and not contradicting...
If you buy a second hand hardware wallet that was
NOT tampered with, it is usually possible to just wipe it and generate a new seed phrase. If you'd do this, you'd be safe.
If you buy a second hand hardware wallet that was tampered with, the RNG might be intentionally broken (or the complete system might be replaced), so it would not matter if you'd receive an unitialised wallet or a pre-initialised wallet (by the bad actor). If you re-initialised said wallet, you'd always end up with derived private keys that could also be found by the bad actor, since the botched RNG would only be able to make a certain well-known preset list of seeds
/master private keys.
The problem with buying from an unreputed (or second hand) source is that you have no way of telling whether the hardware wallet you received is genuine and untampered with... Re-initialising is easy, but it would only safeguard you if the wallet you received was genuine and untampered with.
Bottom line: only buy from a reputable source, check if the package is still sealed, and even then make sure you follow procedure to check for genuine hardware/firmware (if available from the official vendor). Hardware wallets are relatively cheap (certainly vs the current FIAT price), don't risk your funds by cheaping out and buying some refurbished HW wallet, or a HW wallet from sources that are either unknown or don't have a good track record (for example, amazon). Those couple bucks you saved might end up costing you everything helt on the HW wallet.