Question 1: If my exported edited files were not added to the current catalog, where are they (from Lightroom's perspective)?
By default, export is a 'perform and forget' process. You export a derivative file from Lightroom, and Lightroom is no longer involved in what happens with the exported image. So 'from Lightroom's perspective' exported images do not exist, unless you add them to the catalog again (which basically means importing them as a new image). The idea is that you should export in a file format and an image size that is specific for the intended use of the exported image. The next time you need that image for something, you export it again, and again you choose the best file format and image size for the new purpose.
The best example is if you export an image for use on your website or social media. In that case you'll export a fairly small image in sRGB color space. If you decide a few weeks later that you like this image so much that you would like to order a professionally framed print for on a wall in your home, then using the previously exported image for this does not make any sense at all. You will have to export it again; this time much larger and in AdobeRGB, to get the best possible print quality.
That is why I personally never add exported images to my catalog. It simply does not make sense from an organizational point of view in my opinion. I simply export it again each time I need it again.
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