I've modded in three new plants and associated alcohol to play with.
Upon ingestion, each transforms the drinker in a different way. One turns them into a generic werewolf I modded in, one into a dragon, and the last into a GCS.
I set no end time on the transformation, so it's permanent.
Here's what I've found:
1. Guys that were hungry and thirsty before transformation had the same statuses, since my transformations didn't grant NO_EAT or the like. Once I released them from the transformation rooms I built, they ran straight to the food stockpiles and ate. Dragons and Spiders running right into the food stockpiles.
2. Once transformed, the creatures are considered dwarves for some things but not for others.
Are considered Dwarves:
-Guys that were in the military before transformation stay in the military in their new state. They still spar. Right now my Giant Cave Spider Militia Commander is teaching an axedwarf. If I assign them to a station or a kill order, the transformed guys obey.
-Some citizen dragons returned to their bedrooms and hung out there, since they don't have jobs anymore.
-The dragons and spiders obeyed the burrow they were assigned to before they transformed.
Not considered Dwarves:
-I can't change their labors any more, their labors screen now has a standard slaughter order.
-I can assign them to chains.
-They don't show up on the units list for dwarves, or when assigning furniture other than chain an animal/cage an animal, and they show up in the animal listing the units menu.
-I also can't ADD transformed dwarves into military squads.
What this means is that you have to plan ahead of time what you want your transformed guys to do. If you want a squad of them to command, or a burrow for them, figure that out beforehand.
3. I don't know if the dwarves turned murder machines are smart enough to use their newfound fighting powers, such as the webbing and fire interactions. Next Goblin siege I'll mobilize them any find out.
I can't tell if my Giant Cave Soldiers are gaining stats from sparring, since I don't think GCS raws have CAN_LEARN, but are they GCS's, or are they dwarves for that purpose?
EDIT: My Militia Captain is now a dabbling biter thanks to his sparring training, so these guys are learning even post-transformation. This means that if you transformed your dwarves into a fire imp for example, and using their fireball interactions would train their archer skill, making them faster and have better accuracy.