Obviously right now we don't have arena yet, but I thought it would be good to discuss this ahead of time.
Personally I think the game works well in all players counts, but I anticipate people wanting it to be more 3/4 player than 2 player based on other similar games. There is one problem, for less popular games (hopefully won't be Terra Nova) it's much harder to get games with more players and the queue times get longer and the problem snowballs, because fewer people play arena, because of longer queue times.
There are 2 settings that I think are mandatory for competitive gameplay.
1. Faction board: Factions selected in player order
2. Turn order: Variable turn order
Of course the 2nd one doesn't matter in 2 player game, but I think it should still be on, because it's just easier to see with the numbers instead of first player token.
For 2 player there are 3 options, I think all of them are good, I think the Planner Variant and No Variant are just a bit better than Lucky Digger for competitive setting, I wouldn't mind seeing any of them to be honest.
With all that in mind I have 3 propositions for the first arena season:
A. 3 player, Factions selected in player order, Variable turn order
B. 2 Player, Factions selected in player order, Variable turn order
C. 2 Player, Factions selected in player order, Variable turn order, Planner Variant
Hopefully Terra Nova will be more popular and we can get 4 player arena in the future also