I did my house using wirbo and 1/2 inch runs from thje manifolds. Worked fine.. The materials came from fergusons.. An expander tool expands the pipe and it slips onto the manifold and then the pipe shrinkis back down.. Best system for pex I think.. I kept the hot water manifold close top the heater and had a couple cold water manifolds near the joist bay keadiing over/under the wet wall.
I was surprised how easy it was. I used 1" pipe for the cold waster running to the manifolds and using the expander tool on the 1" pipe was tough the rest was pretty easy..
If you haven't checked out furgusons plumibing yet, you probably should.. They gave me a big catalog of all the pex stiuff so that I could figure out my plan.. I would question yhour ability to find the components you need for 3/6" ruins..
Ojh, and I am t a total newbie too.. The tool rental was $25/day and it tool me 3 days as I had to do some extra work making the connection to the line entering the house.