What is the difference between an “IDN variant” in the existing Base gTLD RA (approved by the ICANN Board 21 January 2024) and “Variant TLDs” in the 2026 Base RA?

IDN variants are variant second-level names (see the Root Zone Label Generation Rules [RZ-LGR] for more information), and a Variant TLD is a top-level domain whose DNS label is a variant of the Primary TLD's DNS label.