Translation:The Congress has more power than the President.
Needs an article ("the" or "a") before president! Also an article is not needed before "congress".
i am constantly missing sentences that have quoc hoi in them, because we do not usually use the article "the" in front of it, we just say Congress. Thus, I translate: Congress has more power than the president, which is how we would say it in the United States. And then it's wrong...it's not just this one sentence, it's ALL the sentences in the program that have Congress in them...and there are some other words like this as well, that I can't think of at the moment, but I consistently get marked wrong translating it into English as it is spoken here.
You need a word to describe which way you're going. So it's either "có nhiều ... hơn" ("have/has more ...") or "có ít ... hơn" ("have/has less ...").
Your second question is more complex. It's true that something can have a higher degree of a power or possesses many kinds of powers. That being said, I think "có nhiều quyền lực hơn" means more power. If someone wants to say "... has many more (kinds of) powers...", then they would say "... có rất nhiều loại/thứ quyền lực...".
I hope that helps!