Regarding my question 1 - just now I've got situation, showing me clearly that Buffer has effect for tables with tables in cells (not only for scalars in cells, as I wrote earlier). Sorry guys, who probably read this discussion, for different information. But I (as ordinary PQ user) have access only to interpretations, not to facts (which are program code)...
And overall feeling is that in case of deeper tables Buffer doesn't have effect for deep structures. So in case of cells of type of Record with tables, Buffer didn't help me (but again this may be misinterpretation).