My question is why are there 27 key pairs in electrum for one wallet? [..] Is the balance split up amongst the keys?
Yes, a wallet is a collection of private keys their corresponding addresses. Best practises for making transactions includes using a new address every time you receive bitcoin, and almost every send will also generate a new 'change address' that your wallet software controls. Any wallet that is used to transact will end up being a collection of keys, unless it is poorly coded. Search for 'bitcoin address reuse' to learn more about why this is the norm.
Do I choose one and convert that?
By choosing one, you will be storing that specific address' private key, and none of the others.
If you would like to make a physical backup of your entire electrum wallet, then you should make a copy of your mnemonic seed phrase. This seed phrase is used to generate your master private key, and each subsequent private key your wallet generates will be derived from this master key.
I don't know your exact intention, but I think it is worth mentioning: the usefulness of a cold storage paper wallet is that it is preferably generated on a machine which never connects to the internet. This helps protect your keys from 'hacking' attacks, largely reducing the attack surface to physical breaches (ie someone breaks into your house and steals the physical paper wallets). So creating a paper wallet that is just a copy of one of your electrum addresses does not give you any additional security (rather, it would increase your attack surface). In general, this is why there probably isn't a good tutorial for 'creating a paper wallet that matches a software wallet': the best way to back up a software wallet is to store the seed phrase! Using paper wallets to do the same adds unnecessary complications.
Also worth mentioning: do NOT input your private keys into the website you linked that does private key format conversions. If you must use it, you should save the html file and open it in a VM or offline machine.
