There are people who swear by 'small cell' size, advocating that varroa don't so as well in smaller cells. Lots of controversy over this philosophy. But, on the main, there are fewer advocates nowadays and there is no science supporting small cell that I know of. Bees will make the cell size they want according to their immediate needs, whether it is foundationless, as above, or with foundation.
The size of cells on the first foundations was determined a long time ago by measuring cells of the day. That plus a desire for a larger bee saw some effect on foundation cell size (i.e., from 5.1 per inch to 5.4 per inch) -these numbers vary according to the source you read. Most of the controversy over actual "natural" cell size extant at the time is a result of different ways of measuring the cells. Which way did a given scientist/foundation maker use to record cell size 100 years ago? Nobody really knows for sure, but there have been some loud discussions about it. JMO :-)
P.S. I typed this response last night before Tec responded, but was interrupted and did not post until now. :-)
P.P.S. I bristle anytime I'm reading about bees and see a guru with a more "natural" way of doing things.