> Vietnamese is one example. Having tones attached to syllables means that words and sentences are shorter.
This does not entail that more can be expressed than other languages. Please see my other reply which goes into (admittedly only slightly) more detail.
Yes, sure, "expressability" is something that is hard to quantify.
Otoh, there should br some connection between grammar complexity and written culture. It is my hypothesis but, say, culture with a rich novel writing tradition leads to a complication of the language grammar. A 3 page long sentence, anyone? One can see how Middle Egyptian literature made the underlying language more complex.
This does not entail that more can be expressed than other languages. Please see my other reply which goes into (admittedly only slightly) more detail.