Receptacle Cover Plates & ISOCLEAN Alternatives?

I have five unused receptacles in a dedicated 20A room circuit (I built the house and am a GC). Was considering removing them (they are all off pigtails) in an effort to reduce overall resistance through the circuit and placing brass cover plate over the openings. Have you guys who have done similar experienced any notable benefits?

Noticed ISOCLEAN used plated copper to reduce EMI/RFI. What are some cost-effective alternatives (e.g. manufacturer of nickel plated brass)?