I have heard it said that folks vaping with COPD can find high VG juices to cause a "heavy or congested" feeling in the lungs although not actual pain, and I can't SUBSTANTIATE that with anything.
You are kind of in a pickle given you have COPD and it could be a LOT of things (I myself was ALMOST dx with COPD well it was coming, anyway) but I was also PG SENSITIVE, not VG sensitive. So, it's just hard to say.
Things I have generally heard advised for COPD vaping;
MTL setup, lower volume of vapor higher PG, higher nic (Unless in fact you are allergic to PG, in which case you'd need high or max VG).
If the COPD is advanced, there is the option of Mouth to nose vaping, inhale, hold in your mouth, then exhale through mouth and nose. I don't know if it's necessarily the MOST SATSFYING way of vaping, but your mucus membranes DO absorb plenty of nicotine and vape, so that may be an option until things settle down.
Swedish snus (sold here under the name "general" snus) it's a harm reduction product that has gained a fair amount of traction in Europe and now even here. It's a small pouch that you tuck into your mouth where it is more comfortable. Some folks swear by it, I tried it for the first time yesterday, will be potentially working places I can't vape frequently and etc.
Above all if nothing is working consult your pulmonologist for suggestions. Because I WILL NOTE ALL of the above, I've heard, sometimes people report success, etc., but it's more anecdotal and I am not a doctor and etc.
Best of luck,
Anna