Hi MedienHusky,
The goal is to be able to do without IDs completely at some point in the future and to use only classes instead. This is not yet the case, but it has no effect on the performance of your pages whether the “ID classes” are there or not.
Of course, you can also add your own ID or classes to an element and style it.
.brxe-text-basic or .brxe-heading, on the other hand, are enormously important, because how else would we know what element it is in the first place? Somehow the elements must be identifiable as element x or y.
frontend.min.css/frontend-light.min.css contains all Bricks default styles. We don’t have a list or something, as we’re not a utility class framework 
What do you want to use the classes for?
Best regards,
timmse