check the BCH box when signing to move the coins.
That only really works if you have not moved any BTC post fork or rewind your chain back.
So if I moved a very small amount out of my online Armory Wallet. And haven't touched any of the offline coins. I have to go through some complicated process for both wallets?
The explanation is this: Any BTC you have moved post fork will put your BTC DB is a state that makes the coins inexistent on the BCH side. Any coins you did not move, you can use the BTC DB to create a tx for, that will be valid on the BCH chain.
Therefor, to guarantee you have BTC DB state, you'd have to rewind your blockchain data to the fork point and sync a new Armory DB against that copy of the chain. Otherwise, bite the bullet and sync a BCH node, then build an ArmoryDB against that.