By checklist do you mean options and things you should have included because there are not a lot of variable options in the models offered. I do not think they are doing user defined P8s for 2021 any more.
That said.
1. make sure you get 3 keys 2black 1 orange) Make sure this is what you are getting before you buy it.
2. get them to set up voc for you. Sure you could do it at home, it might even work but best to get them to do it
3. You want a heat pump (but I think this is default for their packages)
4. Ask about the free charge point stuff (hopefully someone here will say if this is still available)
5. Realize the P8 can be quirky at first and some folks have had problems with ac and the display screen. Both of these problems are fixable now but it is good to know.
6. Further realize some things do not work yet. Apple/android CarPlay. Siri’s radio. Ask for a list of what is not working yet

7. Get the car and have a wonderful fun time driving it

it is a blast to drive.
Cheers