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This isn't a direct answer to your questions, but you should be aware of that to maintaining isolation means careful design off the PCB as well.

You would do well to remember that if you are planning to have two isolated grounds you have to arrange everything so that the isolated grounds (or their other signals) do not touch in unexpected places due to shielding, mounting hardware or conductive actuator or sensor housings as you would then loose your isolation or worse yet cause ground loops or loss of noise or safety protection.