The difference between perfective and imperfective is constant, and upheld in any and every case.

Я хочу пить/выпить

The difference depends on what/how you want to drink; and both a viable translations for "I want to drink"
Roughly, the difference is like "wanting to spend some time drinking"(progress focus) versus "wanting to have a drink so that you'll have had a drink"(Result focus)

The выпить meaning alcoholic beverage is for all intents and purposes contextual, and not something to worry about. Just like in English when we say "drink", it can contextually carry alcoholic meaning.

All in all, it's perfectly okay to move ahead past gritty specifics, and just re encounter them later, from another direction. After all, most everything has to be put into real Russian context in order to be properly understood, i.e. when you see a couple movies where they talk about drinking, your brain will capture and abstract out the important patterns for you