I don’t have your particular rig, but if you’re looking for the CAT features, then yes you’re correct as your rig uses RS-232.
If you’re just looking for the audio to do digital modes without CAT features, then you can use JUST the audio cable with the DigiRig regardless of the DigiRig’s serial configuration; I’m doing this right now with my FTM-500 - audio only, no CAT, with an ICOM configured DigiRig Mobile.
Do NOT plug the serial cable into the DigiRig until it’s been confirmed/configured to RS-232, as the voltages are higher than the other signaling modes.