Your'e right, the framed text boxes were not there when you started from scratch.
They are created dynamically when a service is selected in the upper list and when the value was empty, it wasn't shown.
Automatic vs. manual:
"Automatic" search mode is used when pressing the "Start Search All" button, as you guessed, and "manual" search is done when clicking the "Search" button in the lyric editor that is shown when a lyric is clicked in the main grid or if you right-click the row and select "Edit/search lyrics".
The "Delay between searches" is there for the reason, you mentioned.
I haven't found an optimal value; mostly because I've abandoned AZLyrics for the automatic searches and because I am banned for a couple of days and am worried that they should ban me permanently...
I do not recommend the AZLyrics for automatic searches, it is fine for manual searhes, though.
When using the automatic searches, I suggest you start with a short playlist and make your own quality control on the "hit quality" of the different lyric services and then adjust the order of the lyric searches accordingly.
The reason for this is, that the automatic search takes the first hit found by any of the services and stops searching for more.
The fist hit is not necessarily the best for the song, it might be far off the mark, in fact.
Tip: when the automatic search is done, I suggest that you sort the grid by clicking on the lyric column header.
This way the "Found" lyrics are grouped together and the quality control is easier to do.
In the next version coming up shortly, probably this week, you will be able to edit the "credit notes" yourself (the text you call "junk").