Leo,
We tend to make our groups columns here at PowerScore regardless of number, unless there is a special reason to do otherwise. So, for an example game with 2 groups as columns, see here:
https://forum.powerscore.com/lsat/viewtopic.php?t=16406
But here's a game with 6 groups, set up, again, with the groups as columns:
https://forum.powerscore.com/lsat/viewtopic.php?t=11371
Number of groups alone will not determine the orientation of a Grouping game. If it's a pure Grouping game, as in the above examples, we tend to use columns for the groups, as shown. If it's a Linear/Grouping Combination game, then the Linear base is usually what determines the orientation, with the linear element tending to be done horizontally.
The choice of a horizontal vs a vertical base is usually entirely arbitrary for Grouping games. For Linear games, there is sometimes a good reason to choose one orientation over the other: "6 layers of a cake are stacked on top of each other" invites a vertical setup; "7 families live in houses along a street that stretches from west to east" invites a horizontal setup. With pure Grouping games, you'll tend not to have those factors that invite certain orientations of setups.
Robert Carroll