Indeed this plugin is horribly expensive. This one and even X-noise are not much useful for today digital recording where the noise can be kept very low.
I agree, it´s more useful for editing old analog recordings (tapes, gramophones etc..)
The learning function is useful when there are noise only at the beginning or the end of the track so that the plugin can acquire the noise spectrum. In such a case, like here, I always use it. I hear a high frequency loss from your file with respect to mine for the movement that we processed both. However I cannot say that this is because I used the learning and you did not. It may be also due to my noise removal settings being more cautious than your ones.
I´m sure your settings must be more professional, because I don´t know too much about the details (I haven´t taken the time to explore them until now, but I will do in future for sure).
If there is noise at the beginning and the end, I always set a marker directly at the beginning of the first wave and put silence in before the music starts, at the very end I also often put silence in respective I use the "fade-out"-function to create a softer ending. But probably all that is very layman-like as I am in these matters.
For your second subject, I answered you in your Bach topic.
Thank you so much, Didier!