The seed is all you need.

Want to test it out? Download Electrum on an android phone or tablet (or another virtual machine). Turn off data and wifi. Run it. Do a "I have a seed" and let it create the wallet. Notice that the first 20 addresses are the same as the first 20 in your original Electrum wallet.

You can then wipe all program data and storage (or factory reset the device) and it'll all be gone. If it's a VM, just nuke it.


There are other things, like the Extended Master Public Key, this allows you to make a watch-only wallet. You can see everything, but can't spend anything.

If you can somehow get the Extended Master Private Key, that functions just like the 12 seed words. The seed words may be easier to remember or write down. If you're not concerned about using legacy compatible segwit addresses, you won't need this private key; just stick to the seed words.