Depends a bit on which species, Baryancistrus L200 are slightly smaller than Hemiancistrus. Best specific growth information would probably come from a breeder (I don't know whether Baryancistrus have been bred). Neither are fast growing. I've gotten Baryancistrus at 4-4.5 inches, takes me near a year for them to put on another couple of inches or so. I've gotten Hemiancistrus at @ 4.5 and they grew a bit slower. Experience will vary partly because people keep them in different conditions, often based more on the other fish in the tank than L200 preferences.
Would a 2-3 inch pike be able to outgrow and eat a 2-3 inch pleco?