I do believe FATF and VATF are the same and usually have a small beak like jaw structure and are very colorful at a certain length alot of red or orange and almost always have that rainbow scaling affect from the top down. Prominant teeth that are very structured and equal length in size and how far apart they are.
Brevis generally have more body girth and have a missile like shape.
I have seen Brevis with a yellow/greenish tummy or back, never really a yellow tail, and the stripes on them are usually very apparent and less prominant teeth that don't seem to really keep to any uniformity. This is one of the smallest and slowest growing ATF, and generally the least seen on the market because I really don't think there is an interest for it, so I believe it to be somewhat of a rarity.
If anyone owns one, has any other info or better info, please chime in!