Or do I need to worry about input/output?

In other words, can I hook my pipes up in a big line to all my rooms if I want to install plumbing in each, or do I need to have a closed system for the output to my dumping pipe, intersecting at every water fixture?

Also, is there any problem with putting my "non-hot water requiring" items downstream from a boiler/heat store? It seems like it only uses it when necessary for bathing, right? Or should I split off a toilet specific pipe line "upstream" from the water heating rig?

In other words, am I overthinking this or should I just connect everything up like wires do?