Re: UIUC Math+CS - I see what you’re saying. I looked at the 5th year masters info, to see whether that would be a solution to gaining access to additional higher-level CS classes, and it specifically says it’s open only to CS students in the College of Engineering. With all of your advanced standing, you’d be a great candidate to complete a masters without even needing a fifth year, and it would be a shame to be shut out of that option right out of the gate.
Honestly, you are going to do great whether you go to a “reach” or a “safety.” If you scan the resumes of CS faculty at top programs, you’ll see plenty who did their undergrad at schools like ASU, Utah, and Nevada-Reno. CS is very meritocratic and your abilities will show. You’re approaching your search in a very smart, pragmatic way, and I’m sure all will go well for you no matter where you land.