Well, how about the Berkeley Out-of-Order Machine [0] (BOOM)? It's superscalar, out-of-order RISC-V design (one of the very first ones, in fact), and the documentation is fairly detailed. Read [0] and [1] for the general introduction, and then move down to the "Core Overview" section in the left navbar: "Instruction Fetch", "Branch Prediction", etc.
Also, here [2] is another, much more detailed explanation of an O-o-O implementation of a very simplistic RISC ISA which nonetheless has most of the relevant RISC-V features. There are also some other related texts on this subsite [3], including a single-cycle and a pipelined implementations, for the comparison.
[0] https://docs.boom-core.org/en/latest/sections/intro-overview...
[1] https://docs.boom-core.org/en/latest/sections/intro-overview...