If you do go to UNC-CH, start preparing for transfer applications to other colleges where you are likely to be admitted for CS (e.g. most other NC publics other than NCSU, if you need to keep costs to in-state levels), in case you do not get admitted to CS during secondary admission.
The lack of transparency in CS major admission at UNC-CH suggests that it is probably a reach with far more applicants than spaces, so you should assume that it is more likely than not you will not get into the major.