I've noticed this from the start, that when I go from falsetto to normal or vice-versa that my voice will sometimes crack because the air isn't circulating properly. Is this bad? I'm not feeling any strain, just that sometimes I sound like I did when I was 12/13 for a split second.

It doesn't happen as much after I've warmed up, but it still slips every now and then. I'm not quite sure my vocal range, I can sing the notes and I don't give it much thought from that. I can't go much lower than F on the low-E string (sometimes I can get the E or a low D) or much higher than the C note on the 10th fret of the D string, sometimes I get the D... if that helps.

Will it go away with time? It has gotten better, maybe it's jus ta practice thing?

So your range is F2-D4 if I'm not mistaken. What you're talking about, the sound of a 12yo as you call it, is called falsetto. That's absolutely normal. It won't go away with time unless you practice with the correct exercises. But yes it can be fixed.
it's normal that your voice cracks while flipping from full voice to falsetto as the vocal folds have a change of configuration.

To smooth out the the transition, you can find out about "mixed voice".
A tricky exercice to build up control is also the "messa di voce" exercice : you sing a pitch softly in falsetto, then you go louder until turning into full voice, then you go back into falsetto