buckeyefarmer
Epic Contributor
Typically, interior walls aren't insulated, but its a pretty cheap 'quality of life' thing to add during planning/construction, but difficult/expensive after the home is built.
The thing with plumbing, it's just more cost effective is your design can have fixtures back to back (not 100% back to back, just on same wall, opposite sides, near each other) on a common wall; less slab penetrations, less pipe, less roof penetrations for vents, ect. Not the end of the world, and not always possible.
I will use pex, and not really worried about plumbing run length.
In my current house I have only 1 plumbing stack thru the roof. I tied everything together in attic.