Ouzo is flavoured with anise oil. Anise oil contains a chemical called trans-anethole, which gives anise oil its liquorice flavour,
Trans-anethole is soluble in high concentrations of ethyl alcohol, such as occurs in pure ouzo. However, trans-anethole is insoluble in water and when water is added to ouzo, it rapidly forms a milky white oil in water microemulsion.
Incidentally, some cheap types of ouzo are flavoured with synthetically produced trans-anethole, bypassing the need to add the relatively expensive anise oil during distillation.
PCMX is fairly toxic and IPA even more so. Rest assured, if Ouzo contained either, you'd either find yourself in hospital or end up dead.