The checked out thing is not necessary since I believe that locks the file from editing by other larian people. A solo modder wouldn't need that and the checkout function doesn't do anything in the public editor anyway.

You can create speakers though anyway through the speaker manager, it's one of the buttons on the toolbar. Speakers aren't strictly necessary but can be helpful for assigning dialogs in the keyword editor. You can still do it without them but you can only keep track of them by speaker number.

Not sure on the template, I would check the extracted main pak file.

You can probably straight up take the speakers.lsb file from the MAIN pak and put it in your mod as well. That way all the voices would be properly attached. I just remade them to my own liking using the voice acting sheets you can also find in the pak files.