In comments related to this question, there was discussion about pH, fructose concentration, what compounds a fruit contains, etc. influencing or determining "flavor".
Much more recently, I had a couple kiwifruits, which seemed to have a very sweet flavor but left me with the feeling of a mild acid burn on my tongue and lips, similar to the feeling of eating too much fresh pineapple. Both of those fruits are listed as Acid fruits here, along with strawberries (which have a flavor experience of being sweet and not acidic).
This question indicates that the perception of acids in food is more a function of how many anions are in a food (as a % of total molecules), not the pH. At the same time, pH may be important for certain chemical processes in food preparation.
This question, among other sources, frames sweetness and sourness as opposites, and strange (but common) to put together in a dish - yet these two seem to be together naturally in some fruits (e.g. kiwi & pineapple as discussed above). This question suggests that sugar masks perception of sourness (but not acidity) and this one suggests sweetness actually reduces sourness (but not acidity), rather than just masking it.
Is there any connection, linkage, or correlation (even if negative) between sweetness and sourness, ideally based on an understanding of what attributes in a food underly these? Are they independent of one another?