I feel like you're going to run up against the definitions of "efficient" and "compression".

For example, a language with a larger alphabet will be able to express more in fewer characters. Is that more efficient?

Similarly, you could think of each word as a sort of lookup table for information in the mind of the reader. We don't define words as we're writing, we expect the speaker to know them already. If a language has more words, each word is more precise, and fewer words can be used to express an idea—but is that efficiency? You're just relying on the reader having more preexisting knowledge.