RA is an autoimmune disease (AID), which you know, of course, but AI diseases are not like others. If you come down with strep throat, pneumonia or any infectious disease the symptoms and effects will be well known and reasonably predictable. But it seems to me that any AID really means your immune system has gone awry and is not acting as it should. But it's a bit or a lot different for everyone: different symptoms, different reactions to meds, different everything. A rheumatologist who believes there are hard and fast rules for RA to follow is not one I'd want to deal with. It's also likely that anyone with RA has something else going on with their immune system so the RA label is just a general description of what we experience but once the immune system starts acting up it does so in a variety of ways. But it seems to me the bottom line is that once you have any AID you will experience a variety of symptoms because what has happened is your system is broken to some degree but not as your body "breaks" from a clearly defined disease but in a variety of mystifying and mostly painful ways.
Personally I started with Polymyalgia Rheumatica, moved into Palindromic Rheumatism and then into RA. To me I have just had AID and the names mean little. None of them behave exactly as they're supposed to and all together just add up to AID.
Best of luck.