Generally, I like to use 3 lineups.
Reason:
If you only use 2, you have the chance of splitting and just losing overall because of rake. Then you'll be questioning yourself and kicking yourself for not using the winning LU in all your games.
I use 3 with the hopes / expectations that 2 of them will cash, so, 66% is real good and give you a solid return on a given night... If you lose 2 of 3, obviously, you'll lose more money, and the rare cases where I lose on all 3 lineups really does suck, but they are rare.
Overall, if you can stay above 60% long term you'll be fine and slowly build your BR in 50/50s