No, that's pretty close in all regards. Huber is on special assignment so not tied to Utah. I also think it is wrong to think Huber is a solo act. He is no more solo than Mueller is solo. In fact, Huber has greater resources at his disposal.
But if Huber's assignment is linmited to "shadow aht Horowitz is uncovering," then Huber is limited to DOJ (which includes FBI) actions, and does not get to State Dept, CIA and other bad actors. Not to say a SC is warranted for all the others, just noting the scope of assignment matters, and we don't really know what Huber's scope is.
As for what Sessions steps into and stays out of, I think he will follow the correct recusal principles, and may be in some and out of other cases that Huber is overseeing.
There’s also a grand jury in Arkansas apparently ongoing. I’m not sure what they’re looking into, but I believe it relates to the DS.