The effects of caffeine are dependent upon whether you're a slow metabolizer or a fast metabolizer of the substance. Slow metabolizers are the ones who primarily get issues from it: anxiety, extreme dependence and massive withdrawals (stays around longer = higher tolerance), sleep disruption. Fast metabolizers get a boost from it with no side effects. In reality it's more like a spectrum, you can also be just in the middle.
It's why people can't agree on it, you get a different experience depending on your genetics. I've seen slow metabolizers inrl and their dependence on coffee is insane, they start getting the shakes if they skip a coffee and if they decide to quit the withdrawals go on for a week. I can withdraw in about a day, usually a headache, and it's like I wasn't taking it regularly. It also makes no difference on my mood or energy levels if I skip it. I don't recommend doing the ancestry tests but if you've already done it it's going to be in the report.