When it comes to fantasy football of any sort, there’s rarely a single, correct way of doing things. Some DFS lineups are better suited for cash games, and others should be used in tournaments. Ultimately, there can be several methods for generating lineups.
Consider a fantasy manager who enters only cash games. He could make a list of 20 solid lineups without optimizing them for cash games—he's just trying to maximize expected points. After he has 20 lineups, he can select the ones that are better suited for cash games and enter them into his selected contests.
That strategy will probably work just fine, but that seems like a lot of unnecessary work. Why not optimize those lineups for cash games in the first place? He could avoid QB-WR stacks and choose Steady Eddies over boom-or-bust players from the start. Why construct five times as many lineups just to throw 80% of them out?
On the other hand, consider someone who is planning to enter both cash games and tournaments. Now either strategy becomes sensible. He could construct a lineup designed to maximize projected points and decide later which type of tournament to enter based on the characteristics of the lineup. Alternatively, he could construct one lineup that he knows is destined for a cash game and then build another lineup specifically for a tournament.
It’s simply a matter of preference, and readers are encouraged to try it both ways to see which suits them better.