On the difference between constitutional carry vs. permit less carry?

You got me. In Vermont, the state legislature interpreted the US Constitution as automatically recognizing a legal right to carry. Not sure about other states. Off hand, if you use due process to weed out the violent criminals and legally determined nut cases- seems okay. When I was a kid you could buy guns through the mail and we never locked our doors at night back then. We back then we were automatically considered the most free country in the World. Now we are tied with England at number 15, close to slipping under the top 10% level if you consider 190 countries in the world. We are the only country in the World going in the wrong direction.

None in reality.

Semantics mostly.

Though it can be argued that Constitutional Carry is a return to a time when no onerous restrictions applied and 'Permit-Less' carry is 'allowed by the State' to persons not otherwise disqualified.

In essence the 'ability' to carry (lawfully) is basically the same.

Texas has permit less carry.... anyone over 21 (among other stipulations).... i would say the constitution doesn't apply only to those 21 and over.

No, but there has always been restrictions. And it is important to make the distinction between the Constitution and the Bill of Rights.

https://en.wikipedia.org/wiki/Constitutional_carry

I thought the Bill of Rights was just the first ten Amendments to the Constitution, added almost immediately after ratification of the Constitution. Is the distinction you want us to consider that the Bill of Rights makes specific guarantees of personal freedoms?

Very much so. While both the Constitution and Bill of Rights (Which are essentially the first 10 amendments) address the rights of the citizenry....the Constitution for the most part..may be thought of as a right that gives limited power to the state, federal, and local governments. The Bill of Rights expands upon that and spells out the guarantees EVERY citizen is entitled to with respect to Civil Liberties and essential rights.

The way I see it, independent states formed a federal government. These states could relinquish some of their authority (given to them by the people of their state) but they couldn't give this new federal government something they didn't possess. So the Constitution is a document framing THE FEDERAL GOVERMENT. The Bill of Rights therefore is a collection of directives to this FEDERAL government on what the FEDERAL government COULD NOT DO.
What's the difference?
The First says that CONGRESS shall pass no law. What the Federal government COULD NOT DO. Connecticut had a church tax to the Puritan/Congregational Church. I think Virginia had a similar tax for the Episcopalian, etc. There could be no act by the Federal congress establishing a NATIONAL CHURCH. I personally think the 9th and 10th Amendments are not remembered adequately these days. At the start of the country they might have been the most important of all. I am 100% against Slavery but there were around 8-9 cases that went to the Supreme Court and the court ruled that Congress could outlaw the Slave trade into America from other countries and regulated interstate commerce but other than than, the Federal Government had no given authority and it was a pre-existing practice in some states and therefore Constitutional. That's why an Amendment was later needed to abolish it.
So, Christmas tree on a public square in Massachusetts in 1777? US CONGRESS CANT OUTLAW IT. Religious service held at the House of Burgess in Virginia- after Yorktown- US CONGRESS CANT OUTLAW IT. Pre-existing practices and no written authority given to congress in those areas.
Warren Burger argued that regardless of how anyone interprets the Second Amendment- did private firearm ownership exist in all colonies? Pre-existing- the US CONGRESS CANT OUTLAW IT.
The principle of precedent. If you study law to any degree the first thing they tell you is our laws are built on precedent. There is common law to a great extent. Bob cuts through Fred's land. Fred takes Bob to court and the courts rule in favor of Bob because the PRECEDENT is if a person has been doing such for 7 years they earn themselves an easement. Now someone in some other state cites that case and it is held up in court. This goes on for 250 years and pretty soon everyone in America is so regulated that half our freedoms are gone.
You work for the ABC company, as a term of employment you must agree to binding arbitration. Your right to a trial by jury disappears. Some other state adopts that as a PRECEDENT for getting a driver's license, another state for opening up a business, yet another for getting a fishing license or hunting license. I don't know how to fix it but NOW in Massachusetts some small village puts up a Christmas tree on the town square, been doing it EVERY YEAR since 1777 and the FEDERAL GOVERNMENT says it is a VIOLATION of the first amendment. How is that possible? It is a pre-existing condition and Congress was given the limit that they COULDN'T pass a law abridging freedom of religion, etc.
So this PRECEDENT issue needs to be addressed.
In any event the First Ten Amendments aren't the Federal Government recognizing what the People can do, it is the States telling the FFEDERAL GOVERMENT what the federal government can't do and simultaneously also citing rights existing among the people and powers reserved to the States. At least that's how I see it.

Not anymore!!!
https://www.texastribune.org/2022/12/21/texas-handguns-unconstitutional-public-carry/

So, does this mean 18 year olds can buy a handgun now?

^ They already can buy handguns...from private individuals. They cannot buy from FFL licensees unless they are 21.

Federal Law

Federal law is slightly more complicated. There are different age requirements depending on whether you are buying from a Federal Firearms Licensee (FFL) or a private individual, and whether you are purchasing a long gun, such as a shotgun or rifle, or a handgun.

The federal law regarding the legal age to purchase from a FFL can be found in 18 U.S. Code 922(b)(1). It states that a licensed dealer cannot sell any firearm or ammunition to someone who they know is or believe to be under the age of 18. For sales of firearms that are not rifles or shotguns and the corresponding ammunition, the dealer cannot sell to someone who they know is or believe to be under the age of 21. Here, "firearm" is defined by 18 U.S. Code 921(a)(3) as "any weapon (including a starter gun) which will or is designed to or may readily be converted to expel a projectile by the action of an explosive," with the exception of some antique or curio weapons.

However, if the sale is between private individuals, different age limits apply. 18 U.S. Code 922(x) makes it illegal to “sell, deliver, or otherwise transfer” a handgun or handgun ammunition to a juvenile (defined here as a person less than 18 years of age) and for a juvenile to possess a handgun unless all of the following are true:

The juvenile is using the handgun for their employment, ranching or farming, target practice, hunting, or taking a firearm education course
The juvenile has written permission from a parent or guardian who is not prohibited by law from possessing a firearm
The juvenile has the written permission in their possession at any time that they are also in possession of the handgun
The juvenile follows other state and federal laws when possessing the handgun

According to the Giffords Center, federal law does not place a minimum age on possessing or receiving rifles or shotguns.

If you are prevented by law from purchasing a firearm due to your age but are wondering if you can receive a gun as a gift, see: Can I gift a firearm to a minor? How old do you need to be to receive a gun as a gift?

^^ OK, but if the Supreme court ruled that it is unconstitutional to deny someone their 2nd amendment right based on age, then why would that not extend to the sale of said firearms as well?

I don’t know why, write a letter and ask the question.