The tokens stored in my Trezor connected wallet can be viewed without plugging my hard wallet to the computer… Is it how it is supposed to be ? If so, my tokens are safe because any transaction from or to my trezor connected metamask wallet will need to be approved by first connecting the hard wallet (along with the secret keys) to the computer right?
yes so when setup correctly, metamask acts as a view only wallet for the trezor.
outbound transactions will need the trezor to be signed. (unless you sign some sort of wallet draining contract of course)
You will be able to receive incoming transactions without the trezor (but generally always confirm addresses on trezor for safety). And you will be able to view your balances also.
Newbie problems with metamask:
when metamask is first installed it makes you either recover a wallet or create a new one. You can’t just connect your hardware wallet and get started. (this process I really dislike)
NEVER use the trezor’s seed to recover a wallet here, that would mean that metamask would have control of the trezor account directly. Making the wallet from trezor a hot wallet. Which is a bad idea, undoing the whole point of the trezor.
So just create a random wallet and then don’t use it, or only use it for dust transactions.
Metamask can be useful if you think your trezor maybe compromised. You could then recover the trezor’s seed to metamask, gain access to those funds directly, then reset the trezor with a new seed and transfer the funds from the metamask trezor seed to the newly created account on trezor.
Obviously metamask has no idea which tokens you are using, so for them to be viewable, you must add them. Do this carefully as it can be an area where scams occur if you import bad token contracts etc.