My understanding of a fusion is that you might have fine range of motion after a fusion that went well and healed well (bone grew throughout). However, you have to know how to take care of it afterwards, which wasn't explained to me. No jackhammering or splitting logs because force is now multiplied to the disc above or below the fusion. None of the kind of straining work that would blow a disc, because you will blow a disc above or below the fusion more easily than if have no fusion. Sometimes you are supposed to practice using only Eg 70% of your available range of motion to avoid putting strain above or below the fusion. You should get second opinions on these questions and on what you can expect after the fusion from both doctors and physical therapists who have experience with cervical fusion.
Good luck