Which trim should I choose for samurai and 16 x 16 books?

8.5 x 11 (or A4). A samurai page holds five overlapping grids and a 16 x 16 grid has 256 squares, so both need a big page to stay readable. On a smaller trim the digits get smaller; if they fall under 7 pt, the "Ready to publish" card says so and the export stays disabled.