I've set the font-family and font-size in a few different ways before, one of which was:
(custom-set-faces '(default ((t (:family "Liberation Mono" :height 150)))))
However, I learned that if you set it that way, future frames will not be able to use the values and they need something like:
(add-to-list 'default-frame-alist '(font . "Liberation Mono"))
But because I add set it from a variable, I do it like:
(add-to-list 'default-frame-alist `(font . ,custom-variable-font-family))
I'm not able to find a way to set the font-height using this method. I did try to set
height, but it ended up setting the height of the Emacs frame, just like it's mentioned in one of the documentation pages here.
I also tried a few other keywords apart for
font (some from the documentation and some from my own wild guesses), just like you can set the
background-color, etc. But I haven't been able to do that. I wonder if it's even possible (I know it should be) to set the font-height across frames that way.