Hi.
I think it is possible to mix them.
I do not know how fcp sees them on time line as if one of them
has red bar and has to be rendered but generally you should get mixed edit easy.
If you work with lets say JPEG EasySetup then you should have RT but as i do not have mac yet it is hard for me to tell 🙂
—
Margus
https://iconstudios.eu