For a mixed tank I’d go with 3 light bars, 2 blue plus and 1 sky blue or 2 sky blue and one blue plus. Having two of the same over the other will give a different look. If you’re not sure which way to go I would order one of the blue sky and judge for yourself if you like the blue sky or the blue plus better and then order a third strip of the look, you prefer.
For a or an SPS dominant tank, I would suggest five light bars. Two sky, blue, two blue plus and one UV/violet. This would be the best combination if you have an SPS dominant tank and allow you to keep any high light demanding SPS coral with excellent results. I believe this option gives the most even coverage and the best looking color to the eye if you like a blue look to your tank.
As a tip when ordering anything from Orphek use the “contact us“ button and ask if they have any open box discount deals. Someone will reach out to you and I usually get another $10-$25 off from there. Plus they’re offering deep discounts on a new product they have for dimming or ramping the light on these bars if that’s important to you.