Is there a different eTap AXS rear derailleur for 2x and 1x drivetrains?

The larger XPLR rear derailleurs are specifically designed for 1x systems and have the advantage of being able to accommodate larger cassettes.
For 2x systems as well as 1x systems with cassettes 10-36T or smaller, all other 12-speed non-XPLR road rear derailleurs will be compatible.

For more details on the compatibility of AXS components, have a look at out AXS Components Compatibility Map.