What type of discharge will someone get for going AWOL from the NG?

Characterization of discharge is up to the commander. Generally, getting thrown out for unsatisfactory performance - that is what this is -with get you an Other than Honorable.
A review for upgrade is something that is requested by the service member; it is not automatic in 6 years or any other amount of time.

I hope that you are encouraging your brother to do the right thing. Walking away like this is very dishonorable, deserves an OTH, and is worthy of scorn.

It will not automatically change to Honorable. He would have to submit for an upgrade. And....considering he is stating he is just going to go AWOL....I highly doubt the upgrade request would be granted. Your brother just needs to suck it up for however much time he has left then get out. Not to mention the fact he will cheat himself out of benefits for going AWOL and getting an OTH or less.

False. To get your discharge upgraded or your character of service changed, you will have to show that your discharge was “improper" or "inequitable." Improper means factually incorrect or inconsistent with the law. Inequitable means inconsistent with the traditions and policies of the service. Getting a less than honorable discharge is a very bad decision.

https://www.va.gov/discharge-upgrade-instructions/

https://www.nolo.com/legal-encyclopedia/how-get-military-discharge-upgrade.html

He will get an OTH. If he wants to upgrade that, he will need to demonstrate how that characterization of service was inequitable or unfair for being AWOL, and he'll lose that fight.

The VA will make their own determination of benefit eligibility, if he applies.
They may or may not determine he is eligible for any benefits based on his case.

On a civilian job application, an OTH is worse than not having prior military service at all.
And if he lies about it to get hired, and they find out later (they always do), he will get fired for that.

It's a career decision, kinda like getting a neck tattoo, you really limit your opportunities for the rest of your adult life.

This is something that could wind up following him for the rest of his life if he isn't careful. As 1SG (Join to see) stated, it isn't just automatic after 6 years. That's something he'll have to pursue himself, and it's not a guarantee that they'll just grant that upgrade when he submits for it. They can absolutely say no. As long as that OTH discharge is on his background, employers can and will see it in background checks. Most government work is essentially off limits, if he needs to file a claim with the VA down the road for something it's much harder as well. It sounds like you've already tried your best to talk him out of it, so it's not on you SGT Cory Traxler. Stupid people win stupid prizes in the military unfortunately.

Just remember he can be court martialed and spend time in a federal jail as well as and oth his best bet is to talk to his company commander! There are other ways to get released from service that are less damaging!!

AWOL also usually results in a federal warrant for arrest. So, I guess that'll be incentive for him to stay out of further trouble and not to get pulled over by anyone.

Take him to VA hospital and he can whine to the Vets. The one's missing limbs will listen. Take him to a VA National Cemetery and he can complain how hard his life is...they are all ears.

definitley dishonorable RE4

Yes. It becomes a "General-Under Honorable Conditions, then changes to Honorable after 2 years.