The orion will default to a certain SOC when connected. I think its 100%, but not sure. From there it will just start counting AHs. You have the option of configuring "drift" points. Where the BMS will move the SOC to a specific value over 30 seconds or so. The simplest version of this is a 100% voltage trigger (whatever you plan to regularly charge to).
In that same menu you can also set charged/discharged SOC which is only used to run pack state of health calculations.
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With regards to the relay outputs, you can disable them, and just use the BMS to report data to your charger and inverter.