They would have to study flame and ice magic to understand how to make basic temperature changing.
They could probably make a barrier.
The choking with water thing wouldnt work because water is a liquid for other people when touching them, also the making water manipulate is just a simple levitation ability, any witch could do it.
It would be insanely difficult to get the water to go through their nose and into their lungs because I'm sure the victim would struggle/resist. Also that's just levitation, any witch could do it. They would have to study a lot of levitation spells to be able to control and move the small amount of water, and maintain it to travel past the human body entrances. Because the human could just cough it back up easily.
Keep in mind, the more things they have to study, the older they look and appear. I'm not talking 20s, I'm talking they're heading to their late 30s at this rate if you want some powerful abilities that do damage.