If I go to CIET (ROTC Basic Camp), do I still need to go to BCT/AIT for SMP?

This is just a bit more than confusing, but yes, you can go SMP without going to BCT/AIT. However, by going that route, you aren't qualified for GI Bill, or State Tuition assistance if NG, and you don't pick up Time in Service. Enlisting and picking up an MOS, you exempt yourself from the first two years of ROTC, pick up GI Bill to pay for your education, plus any state benefits if National Guard, plus you will get paid as an E-5 Sergeant at Drill and AT as an SMP, and you will be ahead of your peers in experience and knowledge when you hit advanced camp. If you are paying for your own education, I suggest you talk to a recruiter about what is currently being offered in the Army Reserve and Army National Guard as far as educational benefits. It's often well worth your while to pick up BCT/AIT even if it cost you a semester since the immediate benefits when you return will cover most, if not all, of your college costs.

I really doubt that 4 weeks at cadet IET will substsitute 10 weeks of BCT and another 4 weeks minimum for AIT

My understanding is that it is the other way around. If you are going to do SMP, you are essentially “enlisting” into a reserve component. BCT comes along with that. If you are enlisting as a cadet (as in you did ROTC first and tack on SMP), then you don’t have to go to AIT since your MOS will be cadet.

Some ROTC programs make it mandatory for Basic Course cadets to go to Basic Camp, but will allow BCT as a substitute. That may be where the confusion came from.

Honestly, I would just talk to your ROO to get the finer details and see if BCT would fit into your schedule if you wish to pursue SMP.