I have the RT-AC5300 so my band steering will be very different from a dual band router and not much help to you (assuming you don’t have a tri-band router?).
Post a screenshot of your current and I’ll happily make some suggested changes though. Took me a long time to understand the options and there isn’t much good/clear/comprehensive info out there about what they do!
In firmware you can combine these into one and show as only one access point SSID
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