With a gyree you can have a different flow output from each side. Example the right side can flow across top tank for surface agitation and left side can flow towards center of rank for mid tank flow. In theory 1 gyree can act as 2 pumps as far as flow direction
We have one (Redsea 25) in a XL300 (36" wide tank, 65 gall display) along with the regular powerheads. I love this thing. I find it gives me better flow without the jet-engine turbo effect. Our powerheads are probably too powerful, but the gyre creates a feeling like a wall of water is moving through the tank as opposed to a blast from a hose. It was easy to find places where even the mushroom corals weren't annoyed.
I wish I had just gotten like 3 of these instead of the powerheads we have. The low setting on this is nice and LOW and we pointed it at the mushrooms that get covered in sand by our gobies. It is able to gently whisk the sand off without ruffling their skirts.
I run the dual icecap 2k’s in my 50g lowboy. Perfect for such a wide shallow tank the pumps can be run at max without issue though mine max at 50% flow. I have found certain settings to be a PITA. If I allow inverse the pumps make an unbearable reverberating noise, humming in unison. When a pump runs in reverse it is louder, so in my current setting I have the pumps on opposite flows one in reverse while one in forward flow. I am thinking of making both flow the same way and not switching to reverse as it’s starting to bother my wife and that’s the last thing I want. I love the pumps regardless and for the first few days my aged liverock shed tons of sediment that had built up from improperly low flow in previous tanks. I would recommend with caution to expect varying noises with different settings