Thinking about volunteering for Army Recruiting as a TPU E6 with 12 years in. Any recommendations?

I would recommend reaching out to some of your USAR counterparts, maybe call a couple of different recruiting stations and ask to speak to the Reserve Recruiter. My main advice: be prepared to be a 79R until you retire, and if you don't think that's for you, you may want to reconsider. Nearly all AGR NCOs that come out on recruiting are involuntarily reclassed to 79R. You will have room for growth but it will be slower and more competitive than the RA NCOs simply because the higher you promote, the fewer AGR positions there are available. I will say this though. Every single AGR NCO I served for, with, or led was typically more squared away and harder working than the RA NCOs. Best of luck in your decision.

I did that ( over 30 years ago.)
Thing 1= School was a 90 day TDY. If you don’t pass, no AGR TOUR
Thing 2= I as sent to a remote town( good thing) from my home or any military base. My GOV was assigned to me. The RA couldn’t use it.
My RA counterparts were having people tested illegally and two years in the entire Company was relieved. I got transferred to one of the Reserve Units in my area to finish my tour but I was not given any opportunity to get another tour.

It is an experience that I have been privileged to preform. That being said "putting people in boots," is and was one of the most challenging thing in the Army. Be ready for a new perspective Do your homework and Know your competition.