Our house is 80 years old and has pier and beam foundation. We will probably/hopefully live here another 10 years but it could be a "tear down" when we decide to sell. We are in a very good neighborhood (maybe too good for our humble little house). So not sure what our priorities should be as far as pace and pathway to replacing galvanized with PEX. Our water pressure seems to be fine. We are considering whole house water filtration to eliminate chloramine but that is another topic.

Read somewhere on the web that an optimum PEX installation is for each fixture to have a direct line using PEX with minimal number of places where the PEX is broken into from where the water enters the house. (reason to use manifold?) This helps water pressure but also, something that sounded more serious were comments about "leaks" at intersections?

Should we be concerned about minimizing intersections to optimize performance of plumbing fixtures and to minimize potential for leaks or is just okay to have as our goal to replace all galvanized? (not sure if we will have a manifold if we proceed the way we are going.)

I will cross-post this in the OLD HOUSE forum - may be more relevant over there. Not sure.

background/details:

Our old galvanized pipe system is being gradually replaced. Pipes in our newly remodeled bath were replaced with copper. An incoming line from the city to our new external tankless gas water heater was installed with PEX so water would be "clean".

Newly remodeled bathroom copper plumbing is connected to galvanized "network" and then to PEX. I wasn't in a great hurry to fix this as we proceed to remodeling our second bathroom (and then onto kitchen) but now I'm wondering if my phased approach is a bad idea. .
Our remodeler/plumber doesn't do pex so won't have the copper in either bathroom connected to pex plumbing "network" yet - still tied into galvanized to some extent - there is a fair amount I can't explain except to say that I know we must address need to connect PEX somehow (with an adaptor/manifold?) to copper.

I haven't got the right plumber yet for the pex. I had planned to take care of this when we get to the kitchen which is the last phase that involves plumbing. Is it important that I get PEX "interface" done sooner rather than later and at that time, design the plumbing to minimize intersections?