I am planning to visit jiuzhaigou in October, can I get altitude sickness in Huanglong n Emei

JZG will not make you feel uncomfortable as the altitude is not taht high.
Huanglong has a high altitude, and you may have altitude sickness.
But as for Mt. Emei (maybe you are refering to this), you will not feel uncomfortable as well. Just take some thermal coats if you are planning to spend one night on.