ok, Just making an observation here but you only just put round down range with your PT111 and now you're asking about ghost guns. I think we need to take a step back and start explaining differences to you.
A "ghost gun" is any firearm that does not have a serial number assigned to it. This doesn't mean if you grind off the serial numbers you have a ghost gun. You have an illegal firearm with the serial numbers ground off.
Machining vs printing:
When a lower receiver or frame (the part of the firearm that the ATF considers the firearm) is machined out from a larger piece of material such as an 80% lower you have effectively created a ghost gun. Material is removed to produce the lower or frame to accomodate the internal parts. Ghost guns cannot be sold , donated or gifted to another person NO MATTER WHAT. To transfer ownership to another person, the "firearm" requires a serial number.
When you start out with powdered material whether powdered plastics or metals and create the frame from nothing by adding layer after layer after layer, you have a 3D printed firearm. Again, it will be a ghost gun as it does not have a serial number. No transfer of a printed firearm without a serial number is legal.
On both, Once you have the frame or lower receiver, you still need to buy the rest of the parts to make it a functioning firearm. It WILL cost you more to build one from parts than it will be to buy a manufactured firearm. Also, if you decide you want to go this route and build one and decide to buy a fully machined lower receiver for an AR, get one marked as a Pistol, not a rifle. If it's a pistol, you can convert it to a rifle legally. If it's marked as a rifle, you cannot use a barrel shorter than 14.5" with a flash hider or comp or other muzzle device for a total length of 16". If you do, you've created a short barreled rifle and well, without the $200 tax stamp, you've committed another felony. So do your homework and study the legal aspects of everything on top of the mechanical aspects.
And yes, I do have a "ghost gun".. or at least did until that horrific boating accident.