Of course. 2500 is generally a basic course, with supplementary learning of junior high school vocabulary, and of course some are about high-frequency vocabulary. See the introduction of remedial classes for details. 3500 is all the words in high school including junior high school.

Choose according to your own situation. The class capacity of the Oriental Department is generally around 20 people, and of course there are also large classes.

Vocabulary learning generally begins with root affixes, and defines the perspective and usage of vocabulary. Classes in New Oriental generally focus on root affixes and words. I recommend a vocabulary book, English Lexical Morphology, which focuses on perspective. For example, C-camel refers to all kinds of cars, such as mechanical camels, that is, cars, long-distance buses, trolleys in supermarkets, cabs of taxis and so on.

I hope it works for you. Good luck.