Final step since we don't want to broadcast is to delete the signed transaction on PC 2.
At this point I assume the transaction signer is functioning as expected because PC 2 was able to sign the transaction. If I didn't have the right private keys signing would presumably fail in some way, is that correct?
Or is it not 100% assured until the transaction is loaded into Armory on PC 1?
Having it signed without errors is a good sign already but you can still test if the transaction can be broadcasted without actually broadcasting it.
Since you have Bitcoin Core already in the online machine, you can start it (
after closing Armory) and use the command:
testmempoolaccept to see if your node will accept it.
If you're using the default standards, then it's safe to assume that there's nothing wrong with the final transaction.
e.g.:
testmempoolaccept '["0200000000010145_signed_raw_transaction_b700000000"]'