You mentioned Cole Sands in reference to low leverage, which immediately reminded me of USAFChief's principle that in modern bullpen usage there are no low-leverage arms. However, I checked the numbers, and if there is a poster child for correct usage, Sands is it.
baseball-reference.com provides a "Leverage" category in its splits page (for team or for player). By definition, a lot of innings by starting pitchers qualify as low leverage and I am not going to go into that. But if you rank Twins pitchers by batters faced (PA) in low leverage situations, Sands is behind only Ryan/Lopez/Ober/Paddack. When the game is out of hand or safely put away, Sands is the arm Rocco prefers to go to. (Funderburk and Jay Jackson rank highly too, and now they are gone.)
With medium or high leverage, Sands drops behind Duran/Jax/Alcala in batters faced.
And the clincher for me is this: when you slice and dice the numbers for Sands, the pattern of results is stark:
Low Leverage: 127 PA, .497 OPS
Medium Leverage: 29 PA, .661 OPS
High Leverage: 30 PA, .798 OPS
Yes, this is Small Sample Size. I would not stake a lot on this. But the trend is consistent with Sands being used correctly. .798 OPS is losing baseball (from the pitcher's perspective).
I am happy for Sands that he is putting together a nice season. But I don't trust him in an important role and I would not call him a top setup man. It seems that Rocco prefers to avoid such a role for Sands except when the bullpen is otherwise depleted.