I've compiled the chart of all (currently known) alternative forms of Veela.
1) Civilian look. Basically, how Veela looked before getting any powers.
2) Slime form. Generally slower and clumsier than "flesh", and vulherable to being splattered under heavy blows. Seldom used on its own; usually between other transformations or to get into tight spaces. Veela reverts to it if she is exhausted.
3)Mermaid. To be able operate underwater for extended time. All other forms than mermaid and slime require air to breathe.
4)Feral otter. Stealthy, and generally formidable beastie, with a powerful bite.
5)Pony. Very fast, also incorporates Veela's magic wand into itself to serve as horn.
6)Kitsune. Increases all Veela's stats massively, and can change consistency (like melt or become elastic) effortlessly, without losing speed or dexterity. Has nine prehensile, stretchy tails. Veela cannot stay into it for too long and will revert into goo form after prolonged use.
Blender 3.6, Eevee, overpaint in GIMP