Is there a difference between ich fühle mich wohl and ich fühle mich gut? My text book only teaches using "wohl/nicht wohl" and I'm wondering if using 'gut/nicht gut' is also acceptable or not.
These sentences can be used differently. As a German I have experienced the following:
"Sich wohlfühlen" can also be translated to "being comfortable". Often it is used to describe a place or something that you do.
"Sich gut fühlen" on the other hand can be helpful to describe how you’re feeling or when you want to say you are motivated.
"Sich nicht gut fühlen" can also be translated to "feeling ill".
There are of course other usages and many of them overlap - as you suggested.