In 2012, we tried a Rocna on the starboard anchor roller while keeping the factory FOB on the port anchor roller. Major conflict, the Rocna was not able to fully retract and settle and just hanged out dangerously.
The Rocna was returned the same day and a Delta 40Kg installed instead. There is minor conflict with the FOB. The conflict is so minor as to be meaningless. Deltas are "2nd and half"-generation technology, and therefore obsolete by modern standards. We've since used the Delta to anchor out about 500 nights, I'd say. We dragged a number of times during our first year cruising, so we use a Garmin hand-held as anchor alarm.
For peace of mind, we would prefer a Rocna, a Spade, or one of those cool-looking Euro Rocna-look-alikes Amel now installs, but things are what they are.
We've never used the FOB, even though SM2K #350 is one of the few to have a factory-installed second gypsy exclusively dedicated to the port anchor.