The relay board only has value when converting a carby to injection. I have two of then sitting here but have used doner harnesses for conversions for the ease of having more oem connections rather than shop connections, Time and reliability.

When converting an already injected engine, use the harness that came with it. If you can get another harness you can convert it to the MS and then swap it in. This is one way to provide backwards compatibility.
I did pull a connector out of a Mitsu ECU and make an adapter harness to plug the MS into a stock harness. This was nice since the 4G63 seems to act different for some people as far as getting falling edge from the optical sensor. MS1x really needs that.

I think every one that put a LC-1 on a MS got smoke, this was due to a diode in the O2 input that flashed the LC-1. Then I had one die free standing feeding my laptop. Junk they are.

The Tech Edge are robust, all the bells and whistle you will need. If they had the new mini sized one out years age I would not have learned how bad the Innovative products are. I had needed a wideband on a turbo BMW bike.

All my injections run Wideband with full closed loop operation. The dash display is nice but do not tune by it. Theh Edge has an assortment of display types.
With the wideband run into your MS is will be on screen and once you configure the auto tune it will rough in your fuel map for you. From then it will always be there.

Drats big thunderstorm coming, I need to shut down. I will be back.