Yes, you can encrypt any type of file formats and the size of the file or folder is unlimited.
Also, please note that if you have a NordLocker Free account, you can only encrypt 2GB of information to your locker.
The NordLocker application counts how much data you have encrypted during the lifetime of your account, it does not indicate how much space your locker is taking. Even if the locker is empty, the encryption data does not reset.
The size of the decryption is not counted, meaning you can decrypt your files as many times as you wish.