Technically, there is only one type of API key for your account. However, the configuration and usage of that key determine its effectiveness. Here is the breakdown of what is "best" based on your goal.
Do not share your API key across multiple scripts on different IP addresses simultaneously. 1fichier sometimes temp-bans keys that show "aggressive" behavior from too many geographical locations at once.
If you store media on 1fichier, FileBot can use the API to read, rename, and re-upload files automatically.
Treat your API key like a master key to your digital warehouse. If someone obtains it, they can access, delete, or modify your files.