For more higher level code you are probably interested in this topic which explains the internals:
Then for the low-level things this could be helpful:
Do you want to do specific things or do you just want to research and look into different representations, to gain more insights?
Regarding outputting LLVM I think there is also some way to do that, but somebody else will have to point that out, I tend to look at asm or types at comptime via @compileLog, I haven’t really explored the in-between stages.