I still say Ivano Gunther was female, taking on male physical attibutes only because of the melding with the larger Gepelnitch body. Look at those hips! Besides, the character had Sayla's seiyuu.
Mylene was definately Anima Spiritia, just not as strong as Basara. Though in general, anyone should have the potential to switch between spiritia types, as it has more to do with the effort/passion you put into life, than any specific task.
Unfortunately, Exedor is the only giant sized Zentradi on screen at any given time, so there's no real way to get a descent size reference. Refer back to DYRL since he was playing himself in the film.
The effect of Minmay's songs were indeed nothing more than culture shock. Even she realized that by the end of the series, which is why she left to find a true emotion to put into her music (achieved apparently within a year for the Megaroad's launch). In the end, it wasn't Minmay's singing, or the culture shock that saved humanity. It was humanity's willingness to openly share its culture with the Zentradi. i.e. The 3 spies experienced life aboard the Macross, shared their new experiences with their crewmates upon return, and spread like wildfire across the Britai Adoclas fleet. That's why Britai finally made the decision to defect, realizing Bodolza would consider him contaminated anyway, he went with the better option for survival, as well as the wishes of all the men in his fleet.
What Basara sought to achieve was a more direct means of achieving that, sharing emotions/experiences directly through song, not just confusing the enemy with hit & run tactics.