I saw one G9Q in demo model but it is 15 Plus. It had terrible uniformity, half screen was pink and half cooler tone.
Probably the best screen is G9N if you find a good "cut", but there are also bad ones like one we got. Not sure if you can find G9P very uniform, I have never seen one myself.
We ordered 2 x identical 15 PM but one came with G9N and the other G9P. I spent a long time comparing them and eventually I chose G9P for myself but not sure it is really better in everyday use. Our other G9N had more issues with certain test patterns and I initially thought it was worse, much worse especially when turning it sideways (landscape mode) it was very easy to see sides looked totally different tint in NS mode while G9P was about tolerable (not problem free and noticeable worse than my 12 Pro with G9N was). Anyway recently I have few times peeked over the shoulder while other family member uses her G9N and it looks pretty much perfect. Not sure why, is it just that grass looks greener on the other side of the fence or it is really better in everyday use. Hard to say for sure if it is different situation than when you actually get to use each one by yourself like I did when I initially compared them.
My point here, probably if you want to jump to panel lottery and keep exchanging until find a good one, I would aim for a good G9N. Based on this thread and from the 15 PM demo units I have checked myself the most common screen seems to be G9N and G9P and especially G9Q are much rarer. Now recently also many reports having LG screen.