Could you still able to switch from OCS candidate back to enlisted after you already signed the contract?

Where did you read that the OCS graduation rate was 60%? It’s closer to 99%. If a class got anywhere near 60%, the Cadre would be fired. I can understand that you are apprehensive about OCS, but you also failed to do the proper amount of research. Just go to OCS. It’s not that hard. As long as you can pass a PT Test, Height and Weight, and you don’t do anything illegal, or immoral, you will be fine. If you screw up and fail a test multiple times or get kicked out by your peers, that is entirely on you. The tests aren’t overly difficult and you have to be either selfish or incompetent for your peers to rate you low enough to get booted.

go to OCS. It will be unlikely that you make the age cut off later and three years from now you'll be on here asking how to get a waiver.

Go to OCS! The long term pay off for being an officer is much better. More pay and allowances plus opportunities to lead soldiers. Look for an engineer MOS and position. If possible get into Corps of Engineers. Set yourself up for a follow on civil service job.

I'm a bit confused. Are you prior service or is this your initial enlistment? If you aren't prior service and they enlisted you at E-4, the Rank is Specialist in the Army since you aren't in a Chain of Command yet. But that't not t big deal.
What is your goal for going the service and the National Guard in particular? Was it your intention to become an Officer? Your time frame on BCT and OCS seems to about average. I finished OCS is July and didn't ship to IOBC, the version of BOLC at the time, until November. Realistically, a bit over a year from you start point at BTC, depending on the length of you Branch Course.
Success rate at Federal OCS varies, but averages about 90% (I looked it up), but it is also the most competitive to get a slot. That recruiter may have funding and a slot, but it you haven't been through the application and board process, you aren't there yet. The Success rate for the Guard Accelerated program is around 40% and the Traditional Guard somewhere in the middle. On the Guard side, most of those that don't succeed quit and submit a Letter of Resignation. If that was your goal, pursue it. If not, I would suggest doing a bit of enlisted time because you have a couple of years before you would even need a waiver
If your goal was to do some service time and get your education paid for, go that route first. Either wait for your MOS to open up or pick another one. I've found that recruiters can often pull slots out of thin air if they think they will lose a recruit. The recruiter has a mission that does not always mean that he wants to do what you want, but that changes if they know you won't go if you don't get what you want. I had a GT score of 133 and then volunteered Infantry, that is not the jobs the recruiter had lined up for me.
I enlisted Infantry and did almost 3 years enlisted before I went to OCS. I went through One Station Unit Training at 27, and I was not the oldest in my class. I commissioned at age 30. You have time if you want to take it.
The Military isn't College. Courses are designed to be passed, or they are if you know the basic rules. You get to that point, contact me and I will walk you through how to get better than passing scores. My GPA is college was not good, but I finished at the top of my OCS class Academically (tied) and in the top four of my Basic Course. It's learning the Army Way.

Which OCS? The Federal one at Benning is 12 weeks, recycle wasn't bad, I recall around 10-15%. If you can run 5 miles and Ruck 12 the physical part is handled. If you can't today you will be able after BCT. Learn to Land Nav solo, no buddy teams during OCS Land Nav, the big shake out is the history test, but you've crammed in college, you can, and will, pass that. Also, you're going in November, which isn't bad in GA. Gets cold down there in Jan/Feb but you should be done by then. Don't lie, don't cheat, lock your closet. You'll be fine.

If you opted for Accelerated, 8 weeks, it's a bit rougher, but doable. Either way, BCT will set you up for fitness and discipline, people that had hardest time were long time prior enlisted who didn't want to play the games.

Source: Been there, done that BCT+OCS at 33 years old starting OCS in JUNE.

You'll go to drill as a 2LT after OCS while you wait for BOLC. You will like BOLC. I promise.

Stay the course, it will be a good decision. Find something to do in the mean time, six months is nothing in the grand scheme.

If you have the opportunity to become an officer, take it. It's not an easy path, but well worth it.

Lots of great comments that I echo!

Go and push hard to be the honor graduate...

That being said...anything is possible with the right approval person!

Going to OCS right after BCT will permit you to be in the right mindset and level of fitness. Go for it.

CPL (Join to see) to answer your question, I don't know. Honestly I never heard of it. That being said, let me shoot a question your way. What is it that you want out of your military career?

Nothing against the officer's corps, but this is kind of my view on the enlisted vs officer side. You're now or will be a SPC coming into it since you have a college degree, and therefore will become a NCO within a few years. Or you could go through OCS, BOLC, and all that jazz and come out a LT. Either way you're going to be a leader. I see officers and management and NCOs as supervisors, yet at the end of the day, both are still leaders. Like someone else said, it comes down to if you want to actually get your hands dirty and work or manage and lead projects. Either way is completely your choice. If you decide you want to be a worker bee (nothing wrong with that) you can on the enlisted side. Officer side tends to get political.

If you want to lead, do OCS. If you want to be a soldier and do what you're told, don't do OCS. Neither is "better" than the other, it just depends on the level of ownership you want in your military career.