Is there any reason I can not run #12 throughout my shop (110 only) and 20 amp breakers even for the lighting circuits if I stay within the quantity of items per circuit?
Thanks,
Bob

Not sure I understand the concern here, but yes, you can use #12 on 20A breakers for lighting as well as receptacles.
There is NO code limit to number of receptacles on a circuit in a residential setting. Just use common sense.

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