Take for example the word "liquid", which can be both uncountable and countable.
Should it be -
Types of liquid (There are many different types of liquid.) or Types of liquids? (There are many different types of liquids.)
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Substitute a more familiar uncountable noun - coffee.
It is natural and idiomatic to say that 'there are many types of coffee.'
It is baffling (if not nonsensical) to say 'there are many types of coffees.'
Similarly, in an interrogative construction you would not usually want or need to make coffee (or 'liquid') plural.
Which type of coffee do you prefer? (answer - name one type of coffee).
Which types of coffee do you prefer? (answer - name two or more more types of coffee).
Yes. It would mean that you were talking about something you would categorize as "liquids" and their specific types. As such, "types of liquids" doesn't quite mean the same thing as "types of liquid."
After surgery, a patient's diet must restricted to clear liquids. We categorize liquids as clear liquids and opaque liquids. The two types of liquids are clear and opaque.
"Type" is a countable noun and can be pluralized with the addition of s.
Sometimes, "type of" is implied, such as in Benjamin Harman's example "After surgery, a patient's diet must restricted to clear liquids." See Andrew Leach ♦'s comment here: "some non-count nouns can be counted when there are different types or specific instances of the stuff involved..."
If you're using "type" as the countable applying to an uncountable noun, the uncountable would not take a plural form. For example, "We have two types of wine: red and white" sounds a lot more natural than saying "...wines..." unless the speaker is [representing] e.g. a vineyard with several types of red wine and several types of white wine. In the last "e.g." phrase there, I'm also confident of my use of "wine" rather than "wines" with "type" taking the s.