You got some great answers already, but to your first point check out Hennessey and Patterson's books, namely Computer Architecture and Computer Organization an

You got some great answers already, but to your first point check out Hennessey and Patterson's books, namely Computer Architecture and Computer Organization and Design. The latter is probably more suited to you unless you wanna go on a dive into computer architecture itself. There's older editions available for free (authorized by the authors) on the web. I first read the 3rd edition of Computer Architecture and besides being one of the most clear textbooks I've ever read it vastly improved my understanding of what's going on in there in relation to OoO speculative execution, etc.