I have some things I’m printing that I don’t care too much about what material they’re mad of. My CF is almost out and was wondering if it is ok to mix the two. And if so what is the best way to do that? I know BL studio has an option for a second spool of identical material but beyond manually setting the materials to match I’m not sure of another way.
The simple answer? It’s your printer and you can do anything you want with it. 
That is until Bambu Connect decides that they don’t want you using non-Bambu filaments. Hasn’t happened yet but all the pieces are in place do enforce that.
I think your real question is: can you mix filaments in a single print. The answer is categorically yes. In fact, I’ve run out of filament mid-stream running a draft model and mixed filament types and you know what? The world didn’t end. Of course it looks stupid mixing grey with with Black but who cares.
Here’s the original model for comparison