welcome to the forum...
first since you are beginning your quest to carry, i recommend you begin your research and take a look at what the NC attorney general has put out, rev: FEB 2014: (do not look at Oct 13 or previous version).
http://www.ncdoj.gov/getdoc/32344299-a2a7-4ae5-99fd-9018262f64ac/2007-NC-Firearms-gun-Laws.aspx
section III D covers your query about xporting in a vehicle. to paraphase the AG's guidance...quote North Carolina law does not specifically address how to transport a weapon in an automobile. unquote
now that you have read that document you should have a better appreciation on the complexities of NC Statutes concerning firearms.
still curious...here is the NC statute site:
http://www.ncleg.net/gascripts/statutes/statutes.asp
also, go find a NRA basic pistol course in your area and take it! the piece of paper could come in handy if, heaven forbid, you are involved in a judicial situation challenging your abilities to carry and use a hand gun.
to address your judicial comment which i will preface with: INAL!
first things first...please do not post the particulars of your judicial proceedings out on the by ways of the forum as it is public and searchable by al gore's invention!!
1. go to the local courthouse and play nice ask to see and get copies of the documents, all the documents, from your previous encounter with the local judicial system and you now know what the sheriff saw when they denied your PPP.
(there could be several factors in play, one the sheriff doesn't know 14.404 does allow the PPPs to be issued to an individual <21 or they do and is being obstinate and used your history as an excuse to deny until you are >21.
2. compare what the sheriff stated in your denial letter with what you got from the courthouse as well as what you initially got when the event(s) transpired to assure their isn't a clerical error. if there is toddle to the courthouse and ask to speak to someone in the DA's office to see if you can get it rectified.
3. if there are no discrepancies, get an attorney to get the situation fixed, e.g., seal the records since you were a juvie?
now for the hand gun purchase query...
ATF has agreed the NC PPP, as implemented by the 100 county sheriffs, suffices to meet the FBI background checks prior to purchase a hand gun. therefore 14.402 explains the whys and wherefores of getting that piece of paper.
the main reason i personally advocate <21 get a PPP is to give to their caregivers in the event there is any judicial discussion on if you stole the firearm from them and therefore were carrying it illegally. that stated, no you do not need a PPP to OC a hand gun. is there an opportunity you will get hassled by local LE...yes as you have read, even us beaten up adults get hassled all the time doing it.
again, inal, but you receiving and using a handgun from 'a friend' could land the friend into serious federal trouble, using your caregivers yes, friends no.
IMHO, the complication is what is judicially hanging over you and if a LE pokes your name in their computer to check out your 'history' will it cause them to launch into defensive mode or just say, eh, it was youthful indiscretion?
finally, check out NEastern state(s) CCW non resident process as i have heard others successfully follow that path.
again welcome to the complexities of OC'g...
ipse