no, separate... power districts are separate...
so most layouts start as one set of track all connected together, and a single booster feeding the layout.
As the layout grows, if you are using more power than the booster can supply, you can isolate part of the layout and feed that with a separate booster.
You really cannot parallel booster outputs.
A DCC system consists of throttle(s) connected in some way (wired or wireless) to a Command Station.... the brains.
Then the output of the Command Station goes to one or more boosters (that have the voltage and amperage to run locos)
Many times the Command Station and a Booster are packaged in the same box.
I think you are getting a bit ahead of yourself... Find a 5 amp (or more) system you like, and then build on that as you expand.
My layout is in about 4 sections, and about 800-900 linear feet, but I run long trains that take a lot of current.
There are basically 2 loops (so they get 12 amps each), a switchyard (8 amps) and some passing sidings (8 amps).
So I have my layout in 4 power districts running from 4 boosters. My system has 2 boosters packaged with the Command Station. It's a Zimo, and it is unfortunately the highest cost system you can buy, so this is just an example, not a recommendation.
Maybe you can read some on my site: (that is a link below)
DCC
There are 750 separate pages on my site, surf around.
Greg