The download is one archive that holds twelve separate add-on archives in an "addons" folder. Do not unpack those twelve. In Blender: Edit > Preferences > Add-ons > Install from Disk, pick one of the twelve archives, then tick its checkbox to enable it. Repeat for as many as you want, in any order — you do not need all of them, and nothing here depends on anything else being present. There is nothing else to set up: no dependencies, no downloads, no accounts, and nothing leaves your machine. After enabling, press N in the 3D Viewport and the tools appear in the sidebar. If you would rather they did not each take a tab, press Give Each Its Own Tab to fold them under one.

It answers one question they cannot answer separately: can this delivery go out? One run puts every tool you own over every file, opening each file once, and gives you a single verdict, a single report and a single exit code. Running them one at a time gives you twelve answers and no decision.