By default the players are seated in the following order (from top to bottom): Jack (defensive player), Helen (expert player) and Tim (limit maker). The default seat order is beneficial to human player, since Tim, as a limit maker, is not particularly careful with discards, so the human player is likely to get from Tim tiles that he can claim for a Chow (remember, normally tiles for a Chow can be claimed only from the previous player).
Four Winds 2 lets you use random seat order, in which case the computer players' seats are determined randomly when you start a new game.
To enable the use of random seat order:
Using custom face bitmaps