Is there some other meaning in 微笑是一种真实的、热诚的、发自内心的快乐的情绪。?
You are correct, "微笑" (smile) is an "expression" (表情) not a "mood"(情绪)

"happy" (愉快/快乐) is a mood. 


一个微笑 (A smile) 
代表 (represents) 
一个愉快的心情 (a happy mood)



  "微笑是一种真实的、热诚的、发自内心的快乐的情绪。" 


should be 

"微笑(代表着)一种真实、热诚、发自内心的快乐情绪。"

(you can omit most of the '的' to make it less wordy)