Flow requirements for soft corals

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Today I have ordered a 120g Oceanic Reef-ready tank and stand. The plan is to run FOWLR for a few months then start adding corals. The basic plan includes 8 x 54 Watt T5 pendant lighting (Tek-Light), approx 2" shallow sand bed, 25g DIY sump with Euroreef ES-6-2+ or ES-8-1 skimmer, approx 20 gallon refugium for nutrient export, and approx 140 pounds of live rock, adding more later if needed. Also I plan to under-stock with fish in the aims of making this tank as low-maintainence as possible.

The tanks has two corner overflows with a 1" drain hole and 3/4" return hole in each overflow.

From what I have read, hard corals need massive water flow and soft corals don't need or don't like too much water flow, is this right? In addition I have read that lots of turbulent water flow is good to maximize the biofiltration effect of live rock, sweep up any detritus, and prevent accumulation of debris.

Anyway I am wondering about what kind of flow to aim for if I want to keep soft corals and maybe some LPS. I was thinking of a return pump either a "Quiet One 6000" submerged pump in-sump, or an external "Velocity T4" pump, these would go up a 1" line before splitting to the two 3/4" returns.

The questions are:

1. What kind of flow volumes and flow characteristics do I want for a soft coral tank, can I accomplish this with just the return pump, or should I add powerheads or a "Stream" pump?

2. With two 1" standpipes draining down into my sump will the pumps above be a good choice for a return pump or is there a better choice. Heat is not an issue, it is a cold basement and an open-top tank.

Any advice on this would be appreciated.