For example, this chapter:
walks you through this example: What command is run when I press TAB?
How do I find out? How do I find its (elisp) source code? How do I find
the documentation for built-in elisp functions or macros or "special
forms"? All culminating in figuring out (from the elisp source code)
which variable you can set to customise your indentation level.
I wouldn't say never learn two things at once, but I'd be aware of the extra mental load you're creating for yourself. It definitely makes things more challenging.