I'm curious how much genetic geographic clustering could have influenced the baseline associations identified in the UK genome wide association studies you selected as a starting point (not sure they typically control for region when associating traits?), particularly with traits like conscientiousness and openness, which obviously can be influenced by polygenic factors, but are also highly influenced by regional cultural variation.

Yup, take a look at: https://www.nature.com/articles/s41588-022-01062-7.pdf