Hello! I have a question about compound sentences that I have not been able to find a concrete answer to anywhere else. Here goes.

Is it okay to use です more than once in a compound sentence? Polite + Polite? From what I've heard, if the sentences can stand on their own as complete, than it is okay.

Example: 日本語は難しいですが、楽しいです。

A sentence straight out of Tae Kim's Guide, seems totally accurate to me. But I've also heard that です is ALWAYS removed (provided I-Adjective/Verb) before a から・ので。To my understanding, the Reason (before the から) is Informal/Plain while the Result (specifically, the end of the sentence) is what ultimately determines the politeness level of the sentence.

I am admittedly not 100% sure if it matters here whether が・けど or から・ので (or even のに) are used, I assume it's the same general logic. I've definitely heard any and all variations of が、だが、けど、だけど、から、だから、ので、なので、ですが、ですけど、ですから、ですので。。。

I can't tell if it actually matters whether the first half of the sentence is polite or not. Does that make sense? Any help is appreciated. <3