The symptoms appear the same, but the cause seeminlgy quite different in your case. Your spo2 plunges do seem to be caused directly by apneas (as every time you stop breathing and it's marked as an 'oa'). But the question is whether the DreamStation APAP you're using is falsely detecting centrals as obstructives (if, like you say, you feel you've ruled out obstructives as being likely) - it sends a test pulse to see if your airway is clear to establish this but I've always been a bit dubious about the validity of that result. My spo2 levels fall as a result of my flow rate going right down over a period of time, and that's while on ASV. I do have apneas without the ASV, but it kicks in to deliver breaths which is the main difference between ASV (or Bilevel ST) and standard CPAP/APAP/'Vanilla' Bilevel.
I'm not an expert and I'm sure others might disagree or have their own opinion, but if it were me the first thing I'd try doing is dropping your Min EPAP to something like 6 and ensuring you're running in Auto (not CPAP) mode - this should hopefully answer whether a higher pressure is causing the apneas. If this still doesn't work, exhaust any possible positional apnea solutions as advised by sleeprider. Any change you make, give it a few nights to see how your body responds.
If all else fails and you're stopping breathing as a result of centrals which are not induced by the high CPAP pressure itself, you might be a candidate for ASV. But, I'd definitely consult with an RPSGT about that first as they may decide you're a better candidate for ST therapy (usually more applicable where there are conditions like COPD existent). Here in the UK I'm left waiting up to a year before I can even speak to a sleep tech due to the mess covid has caused our NHS, so I'm doing this alone and very gradually / with a lot of research and monitoring my data. I use hospital grade equipment where I can and have arrived at a therapy that seems to safely 'do the job' for me for now, but I will still want a full polysomnographic study - I can however go into that appointment with a catalogue of data I've collected myself.
This is a pretty good video about ASV settings / indications imo: https://www.youtube.com/watch?v=JmCJjDOjYQQ
If you do try and purchase a machine, I recommend any of the resmed adapt SV machines (S9 or above if you want OSCAR/SLEEPYHEAD, S7/S8 are just as effective in terms of the therapy if you can live with only having Resscan to analyse your data). I picked up a refurbed ~200 hours S9 VPAP AdaptSV for $600 and a low hours S7 VPAP Adapt SV for just $200 - both came with humidifiers and they're both awesome machines. But, do as I say and not as I do - get advice first if you can Again, do bare in mind what sleeprider has said - there is a good chance they could be positional apneas looking at the charts... know though that if that's not the case and your problems are central, there are more effective therapy options out there. I decided to try ASV on the basis my DreamStation was flagging the vast majority of my events as central apneas and hypopneas, and my flow rate graphs were all over the place - the therapy is a significant improvement for me over stadard CPAP/BiLevel (which I've also tried), but still not perfect. It's just keeping me out of the danger zone for now.
Chris