So we live on 40 acres (1500x1100 feet).  Our internet starts at the center of the property.  We have 2 out buildings, each roughly 150feet from the other and 150 feet away from the internet.  We also have an orchard that is 250 feet from the internet, and a gate that is 600 feet from the internet.   I have just purchased 4 AC1200's, one to attach to our modem/router and the others to be installed on each building and gate.  I have power at all of these locations.  My goal is to have a general outdoor mesh, as well as provide internet to our main shop which is all metal.  

Our goal is to be able to have wireless security cameras at various points on the property.   

We do have conduit buried in the ground for data, but it seems like too long of a run to get ethernet everywhere without repeaters / boosters.  

So my questions are -  

Is the AC1200 the best / correct choice.  I feel that the only potential issue is the gate as it will be at least 300feet from the other AC1200.  Any other recommendations?  I assume that the AC1200 can act as a stand alone WAP without a directly wired connection to the main router.  Or do I need a bridge and (like an N300).  

Our main shop is all metal (and 150feet from the internet).  I assume I will need to attach a wifi router to the external AC1200 to provide internet inside?  Or should I do something with a Bridge instead?  I will still want to have a WAP outside the building.  

Our internet speed is quite low (15 megs down,1 up) at the moment.  Someday Starlink might come through, but we are not holding our breath anymore.