When using the 'Multi-Lineups' tool in Player Models, you'll see a slider labeled 'Diversification' in the settings on the left hand side of the page.
This slider changes your lineups from being more optimal (0) to more random (10). The most optimal lineups will generally have higher overall ratings based on the model you're using. The more random lineups will likely have lower ratings, but will offer a wider variety of players if you're interested in using a larger player pool over several lineups.