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
No, my question was simply whether it is ok to mix PETG-CF with translucent. PETG is naturally translucent and I doubt adding CF would cause any kind of bonding issue between the two but wanted to make sure. I’m just about to run out of CF so thought I would transition mid print if possible to the translucent.
He did say yes.
I concur.
PETG is PETG, it doesn’t matter if it has CF in it.
PETG can be opaque or translucent, it depends on the blend. There are an awful lot of black food containers out there solely because they make the contents look more appealing, that is true BTW.
That said, you carry the same risk as with all filament blends, even if there are identical in every way. Sheer force.
The point at which they are joined is the weakest point, if only because the time it takes to swap one for the other means the normal extrude and cool is drawn out.
If the join is at a critical point, it will be the weakest point if the model.
You can mitigate this if you use some filament merging routines (like bricks in Orca Slicer, nit currently in Bambu Studio) or add something manual yourself. The idea is to decrease the use of one filament in a layer while simultaneously increasing the next filament across multiple intertwining layers.
A simpler way if strength is the key is to print the model at an angle so the resulting print will be bound by many layers across the diagonal.
If strength has no role in your model, just print away as you should be fine.
The same logic goes for all similar filament types(PLA, ABS and such), mix and match PLA Basic, translucent, CF, matte and so on.