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With modern PCB manufacturing techniques, balancing copper on layers or leaving copper on the top layer is not necessary and does not change PCB cost.
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The important thing for you, the designer, is to have an unbroken GND plane on the bottom, any traces on the bottom should be short and strapped so return ground signals do not need the hunt for a return path the GND.
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Let’s see your latest design to be sent to the manufacturer.
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Now to be clear, these are indeed best practice guide lines. There are 10s of thousands of PCBs poorly routed that still function well.