Hi,
Based on my careful evaluation on project brief, I think generally you would need layout plan for the fire sprinkler system to cover the 4000 sqft (house area, probably two stories) and 1500 sqft (garage).
Feel free to let me know the technical specification of sprinkler radius coverage area, the spray angle, then I can work out the sprinkler per layout - for an example a simple bed room or s small study room, may require minimum one, maximum two sprinkler.
I have come across PEX tube for sometimes, it is widely used in western countries for cold and hot water plumbing system. They drill holes in drywall wood structure to run the PEX tube inside dry wall and underneath floor slab.
Let me know if my knowledge and skills will be able to you with layout plan.
Thanks.