I think you are mixing it quite a bit. SFP+ is still Ethernet, also SFP28 gives you speed (25Gbps) RJ45 will never do, so the extra card for the extra speed is

I think you are mixing it quite a bit. SFP+ is still Ethernet, also SFP28 gives you speed (25Gbps) RJ45 will never do, so the extra card for the extra speed is mandatory.