List of ways to say thank you in Chinese:
谢谢 - Thanks (Northern China) (Xièxiè)
谢谢你 - Thank you (Casual) (Xièxiè Nǐ)
谢谢您 - Thank you (Formal) (Xièxiè Nín)
多谢 - Many thanks (Southern China) (Duōxiè)
太谢谢了 - Thanks so much (Tài Xièxièle)
Traditional: 谢 becomes 謝, only difference in all of the above sentences. You will often see 讠turning into 言 in traditional Chinese.
Is there any grammatical or lexical differences between Traditional and Simplfied Chinese and Which one is Traditional and which Simplified - Mandarin or Cantonese or are those different ones?
Simplified vs Traditional is simply a change in characters. As far as I know, the main places that use traditional are Hong Kong and Taiwan. Any word can be written in either simplified or traditional, whether it's from Mandarin, Cantonese, or some other dialect.
TellowKrinkle is correct. I just wanted to add that although the spoken Chinese varies throughout China, whether that's due to the dialect spoken or whether it's Mandarin or Cantonese being spoken, the written language is the same, whether that's the simplified version or traditional version. Also, the change in characters that TellowKrinkle referred to is that the traditional version has more strokes than the simplified version, when writing the characters.
When my Chinese teacher taught me how to say "Thank you"(she's a native speaker), she didn't include 你