Earlier quoted context omitted.
Caffeine affects people differently… it has very intense effects on me- I would never call it “very very mild”
If I’ve gone a long time without caffeine a single coffee could keep me awake up for two consecutive all nighters. As a regular drinker I still cannot handle more than one cup of coffee per day. It turns out that I have a number of genes that increase the intensity and the duration of effect. I think genes explain most of the differences in experiences with caffeine.
I have only done 23andme not a WGS like you, but I have at least one liver enzyme SNP that dramatically slows down caffeine metabolism. It took me quite a while to realize that the advice of "no caffeine after 5pm" or whatever needed to be something more like - no more than one cup of coffee before dawn.