Thanks, I will give this a shot. Just one thing. I have Coinomi installed, but no wallet set up yet. Clean slate, fresh install. Rather than sweep, can I click "Restore a wallet" on the first screen that pops up, then scan the QR code, then add in a bitcoin gold wallet after the BTC wallet is created with my Electrum Private Key. I thought I saw a way to add the bitcoin gold wallet after somewhere, by choosing a currency type to add, but I don't know where I saw that now. If any of that makes sense.
No. You can't import a Electrum seed nor a single private key into Coinomi.
Or, should I set up a new wallet from scratch, go into the bitcoin gold wallet and do the sweep?
That's what you should do. Create a new wallet from Coinomi (don't forget to save your seed), and them do the BTG sweep.