There are so many coffee varieties, that I don't know which one to choose. Is there any difference between them? Maybe more caffeine in some, or something like that?
No, all coffee varieties will have the same nutritional values, with only minor differences, none of which will be even close to being significant. The main difference is the taste – the alcaloids and their ratio will be just the same.
Forget the coffee shop. There are different beans, dark or light roasts and blends. I like Aribica (I've tried Jamaican Blue Mountain) and I like it dark roasted. I take my coffee black and sweet. Others prefer Robusta etc etc
The lighter roasts have a milder taste but a higher caffeine content. Darker roasts have a stronger taste but less caffeine. Both have a pretty high caffeine content though.
If you like coffee but don't want the caffeine - drink decaf
It is interesting, how coffee can be pretty much the same but with different taste. In such case I guess I can just stick to the best taste, since it makes no difference.