Electrum wallet file Are all the information of my wallet stored inside the wallet file that I can find in the folder "wallet", inside the .electrum folder?

For instance, I can copy this file on another pc and just paste it into the "wallet" folder to have access to my BTC again, right?  (assuming that I know the wallet password)

I know that I can restore the whole wallet with the master seed, I was just curios if this method works also.
Yes. All of the information about your wallet is stored in the file of the same name as your wallet in the wallet folder of the electrum datadir. Copying that file elsewhere will allow you to keep all labels and comments on your addresses and transactions.