Hi Jiri,
We use the IBM COM API option and it seems to work fine. I do not know why this one was chosen as the object was created long ago.
Since you already found the docs for HLLAPI, you might as well use this option. I'm not aware of a preference for one or the other. Give it a try and if you run into issues, just post here again.
Happy coding!
Paul, Sweden
(By all means, do not mark this as the best answer!)