I am building a large chests network to be able to have a "global" storage center that retrieves items from all my diverse farms/generators across the map and lets me access my global storage from terminals in connected locations.

To make this, you would naturally want to use pipe pressurizers to speed up the transport process. However, I have a doubt about how they work.

Do they work like vanilla powered rails (only speeding up some adjacent pipes) or do they increase the speed of the whole network?

Are they stackable? What is the speed multiplier? Is there any sort of effectiveness decay when using multiple pressurizers? Is there a travelling speed limit for items?

If they speed up the whole pipe network, I could simply build a "pressurizing plant" with all the pressurizers connected there, which would also make it easier to supply power to them.

Pipe pressurizers increase the speed for all items in the attached pipe network.

They are not stackable, but their effect stacks with speed modules. This means the maximum speed for a pipe item is a pressurized network, plus being extracted by a pipe with a tier three speed module.