Update - I'm now almost 5 weeks post-creatine. I did anticipate if this problem had been caused by that, it would take 4-8 weeks to fully clear my system, going off stuff I'd read online.
And lo and behold, my throat irritation is now only about a 2/10, if it was a 10/10 at its worst. I'm still leaning towards this as the probable cause, despite the ENT thinking it was unrelated. Too much of a coincidence? The creatine was the only thing that changed noticeably, I formed the hypothesis, carried it out, and it worked. The only other possibility I'm considering is that it is something that built up gradually as a consequence of vaping heavily oxidised liquid for weeks.
I find unless the nic strength is very high, then having the vape liquid be somewhat oxidised (I guess you could call it "heavily steeped") is the only way to deliver any kind of throat hit. And I used to love taking massive DTL rips, you don't want to be doing that with much more than 6mg/ml or you'll just spend your life in a nicotine-stoned haze
But the downside is if the liquid is
too oxidised, it cludges up your throat.
Anyway the good news is I'm recovered enough now to puff on a disposable small vape again, without too many problems, just some mild irritation which passes off. Had to try a few though until I found one I could tolerate. Maybe another couple of weeks back to normal?
I now variously puff on the IQOS, use artificial nicotine pouches, use Swedish snus AND vape a little bit, I'm not sure "chugging nicotine in as many different ways as I physically can" was the original goal of this exercise