I only get options for Streaming and CD when selecting the What Are You Going For option when using iZotope in Logic Pro X. I have my track for mastering and my reference track ready to go within the project so am confused as to why I can't see it. Every tutorial I see seems to describe the option always being visible there, please help!

Hi - You don't say what iZotope product you're talking about, but since you mention mastering I assume it's Ozone. Under DESTINATION in the Master Assistant dialog there are in fact only two options: Streaming or CD (see the screenshot below). As you can see there's a Reference option under LOUDNESS & EQ, but that's only present in Ozone 9 -- if you don't see it you must have an older version of Ozone [8 or earlier].