The advantage of 2-4-6 varies greatly depending on how those first 2 batons go.
Assuming the two teams are of equivalent skill, if the opening team hits:
0 kubbs then they are behind, winning only about 40% of the time
1 kubb then they are winning, carrying the game about 60% of the time
2 kubbs on the opener is absolutely dominating, with the opening team cruising to a victory about 75% of the time.
Interestingly, those benchmarks (40, 60, & 75) hold true over a very large band of performance, from beginner to expert, just so long as the teams are equal. However, as the frequency of hitting 1 or 2 goes up for better teams, the net turn one advantage scales up as well.