Go here to see the middle 50% ranges for the mathematics and computer science major (which is in the A&S college not the engineering college) https://myillini.illinois.edu/Programs/MajorDetail/10KV1438BSLA. The GPA given is unweighted. As you will see your SAT, and I assume based on what you provide, your actual unweighted GPA, likely puts you in the bottom 25% of those admitted and you should assume you are therefore a reach.
Moreover, with UIUC being in-state does not mean you will be favored over non-residents. You can provide both a first and second choice major on the application and, for first choice majors, both residents and non-residents are evaluated on the same basis for deciding admission,. It is second choice where preference is given to in-state. However, you cannot list any computer science major as a second choice.
As far as “easier” majors for admission, if your thought is to apply for something else and then try to transfer later to a CS program, be aware that the CS programs have even lower transfer admission rates than for freshman and you cannot assume any high chance to be able to transfer to a CS major. The mathematics major without the CS actually has a middle 50% range that you would be within although possibly the lower part of that range. A division which has fairly low middle 50% ranges and fairly high admission rates is the the Division of General Studies, which means you would be applying undecided as to major.