If you have neck issues you may already have had cervical (neck) x-rays done, perhaps flexion and extension views? Discuss those with your docs.
You could also do an internet search for flexion extension views, or anterior cervical osteophytes or similar and see how narrow the column or air can actually be.
These osteophytes, if large enough, can sometimes cause difficulty in swallowing, and depending your neck position during sleep could impact the calibre of your upper airways.
You could do a search for DISH dysphagia images for example, or DISH and sleep apnea. Not saying this is applicable to you of course, only your medical team will know, just by way of illustration.
Secondly, excessive muscular exercise can cause edema (swelling of the muscles).
In my younger gym junkie days, if I overdid in the biceps curls after coming back from a lay-off, I would get such bad swelling (edema) I couldn't straighten my elbows for a few days! I remember writing exams (the good old days!!!) without being able to fully bend my elbows. It would take about 3 or 4 days to settle down.
I am sure you are more careful than that, though.
Without a soft cervical collar my pressures and AHIs are on the high side. For me the sleep ergonomics play a bigger role than the CPAP pressures in controlling things: too flexed when side sleeping >>> I get clusters of OSA with chin tucking. Too extended (very flat pillow) this feels uncomfortable. I remember Goldilocks and the 3 bears: it's got to be "just right", and how can I control that when I am asleep?
Nevertheless, each night is different.
None of this is advice, of course, but just some idle lateral thinking. Each of us has to find the best set up for our own situation.
Wishing you all the best in your quest.