Whats the difference? (not between OEM/COEM, rather, why does it make a difference for what you're trying to do)
COEM = Commercial OEM But you can use the iso, l333tisw00t offers, and use daz loader to install the correct key and certificates for legit activation, or implement the Multi OEM/Retail project. You can also install pro/ultimate and genuinely activate them on slic systems