With my usual disclaimer, I cannot give legal advice with respect to the laws of any state except Kentucky.
Whether constitutional carry applies to everyone, just citizens, 18+, 21+, etc., depends on how the law is written.
KY allows any person 18 or over who is not otherwise prohibited to carry concealed deadly weapons. This applies to all deadly weapons, not just firearms, defined by statute not otherwise prohibited by law.
I believe MO applies to all persons and the OK bill I looked at said all persons. One interesting thing I saw in OKs law was that you cannot carry anything larger than .45 cal. And it appears to only cover firearms.
KY deadly weapons:
“Deadly weapon” means any of the following:
(a) A weapon of mass destruction;
(b) Any weapon from which a shot, readily capable of producing death or other serious physical injury, may be discharged;
© Any knife other than an ordinary pocket knife or hunting knife;
(d) Billy, nightstick, or club;
(e) Blackjack or slapjack;
(f) Nunchaku karate sticks;
(g) Shuriken or death star; or
(h) Artificial knuckles made from metal, plastic, or other similar hard material;
Weapons of mass destruction are prohibited by federal law and other sections of KY law.