Yeah, unfortunately the guides are either wrong or being misunderstood. Individual mod files (usually .jar file extension) can be dropped into the mods folder. Those modpacks from curseforge need some sort of launcher to read the modpack .zip file, and actually install the mods/configurations for you. This is also usually just for the client as well, and you usually download a separate package (containing everyting from forge up) for the server. I just went and looked, and it's not very intuitive how to get to the server files. Click the Files link on the modpack page, then click the modpack version you're using in the list, then click Additional Files link at the bottom, and you should see a link to the server package.
Curseforge/Overwolf launcher is garbage, I would suggest some other 3rd party launcher for your client such as ATLauncher or something. Unless you like video ads in your Minecraft launcher.