Could you please tell me, knowledgeable people, would it be possible to place my crypto assets on both devices at the same time and, if yes, then, if for example my Nano X would get hacked, Tangem will still have them? Or, if they are gone from one wallet they'd be gone from all cold wallets, because hacker would authorise transactions for me?
OK, you misunderstood the bitcoin wallets, so let me try to explain.
The bitcoins are not in a bitcoin wallet. Ever. They are (let's say it simple) on the blockchain.
The wallet only holds the KEYS to the bitcoins. The key to spend them, more exactly. Only who has the correct keys for certain bitcoins can spend them (send them away).
And yes, the wallet helps you do certain operations with your keys - usually this means facilitating the spending.
So, if 2 hardware wallets have the same seed will generate the same keys and any of them can be used to spend.
If somebody else will get the seed he will spend/send away all the bitcoins (that can be spent by your keys, so "your" bitcoins) so you no longer have access to them, no matter how many hardware wallets you hold.
Clearer?
