String Loops or Metal Rings?

[Rustywreck]

I'm not familliar with that release, but it will probably work fine.
It won't take you long to become efficient with a string loop. What you will likely find is that your arrow flight is more true, and will need to make a sight adjustment. People often don't realize how much they torque they impart on the string - the string loop will help to remove it.
After you become comfortable with the loop, it probably wouldn't hurt ot check the rest and string nock tuning by paper tuning.