If you have intermittent flares of iritis, that generally isn't associated with PMR --- iritis is associated more with inflammatory arthritis and other autoimmune disorders but not usually PMR. This link lists various known causes of iritis.
https://www.mayoclinic.org/diseases-conditions/iritis/symptoms-causes/syc-20354961
I had recurring flares of iritis and that didn't prevent me from being diagnosed with PMR in addition to inflammatory arthritis.
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With that being said #1 is more likely than #2 but having PMR with something else in addition to PMR is possible. Having one autoimmune disorder increases the risk of having others.

Furthermore, you can't rule out the possibility of #3 and #4. However PMR almost always responds to a Prednisone dose of 15 mg to usually no more than say 40 mg more of less.

Diagnosing PMR is mostly someone's guess because there isn't any exact criteria for diagnosing PMR.

After being diagnosed with PMR and getting on Prednisone --- there isn't any tapering method that works for everyone but first you need an accurate diagnosis.

Most research into PMR has a disclaimer that more research is needed. Everything about PMR is as clear as mud and very confusing.

I was diagnosed with PMR 15 years ago. I didn't finally get off Prednisone until 3 years ago. I have managed to learn a few things along the way but mostly ... I don't know much of anything. I'm just happy to be done with Prednisone but I probably still have PMR.