I think as long as you're below the frost line it's okay just to bury it. if you wanted you could put it in a sleeve of PVC just in case you ever had to dig it up. less likely to cut it i reckon. I found this article but I don't know if it's going to be much help to you.[reevesjournal.com]

I have work with PEX a lot the best way to hook them up is with these connectors they are called SharkBites they're just pressed together tings for PEX and they are awesome again little spendy but gosh they make the job easy

I'm a GC in Florida, I've worked quite a bit with PEX. Not sure I understand what you mean that the coupling is going to be burred, the standard PEX couplings are barbed or "ribbed" if you will. The PEX tubing needs to be cut square, put your crimp ring on the tube and insert the coupling into the tube. Crimp the ring using the crimp tool, there is not any coating or protective sleeve that needs to be over the ring. These tings should not be used under concrete or buried in the dirt. Typically the connections are in a wall cavity, attic, cabinet or some other semi-protected space. Hopefully this helps.