It's same mean. but 나는 used in talk to friend and younger than me in school. 저는 used in all other.

It is not common to use both of them in the same sentence. As you said, they are a different level of honorifics.

You said "in the same paragraph," not "in the same sentence," which makes my reply: "It depends." You correctly understood the basic difference between 나는 and 저는. When you decide which level and/or type of honorifics you use, you must identify your relationship with your audience, and/or subject/object you're referring to. Perhaps it's a quoted sentence. If you have a specific example you can give us, we can be of better help. Thanks for asking your questions!