I have a bunch of old wallet.dat files that are very likely empty. I would love to give a final look to make sure I am not missing any money in those wallets.
Does this give me the full picture of the balance of those wallets?
You can use dumpwallet in Bitcoin Core and import private keys from wallet dumping to Electrum wallet for checking address and wallet balance. Electrum is a SPV wallet and you don't have to sync your wallet for a long time like Bitcoin Core.
I notice big issues in your post. You have some wallet files, and with this information, I recommend you to sync your Bitcoin full node with Initial Blockchain Download first. Then you can check balance of different wallet files.