Hi Atlan,
Please stop posting the same thing in two different threads in the wrong forums (you should have posted it to
addon help instead), but seeing that nobody has answered so far I suggest you move your question on the
official mac technical support forum, as we do not seem have any mac users here.
To answer one part of your question, the operating system has nothing to do with which format a game uses for its textures. DDS files can be loaded on any system as it is just a container and the game will have a library to read it. Changing file formats to something that is not supported by ESO (png) won't help at all.