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Probably you would want to learn about using Path Operations, or also called boolean operations. Inkscape provides those natively, so you might not necessarily need to install that extension.
It depends on each particular image as to which path operation would work the best. Here's the manual info on path operations:
http://tavmjong.free.fr/INKSCAPE/MANUAL/html/Paths-Combining.htmlAs far as I understand, that extension allows to perform multiple operations with one click, while the ones Inkscape provides natively, you can only do one operation at a time. So that extension would help if you needed to, for example, subract (Difference) or intersect (or other operation) with the same object, several times. I guess Moini is thinking you could use the clipping path and intersect it with all the other paths in the image (assuming there's more than one).
But again, it very much depends on each particular image, and exactly what your goal is with each path, as to which operation you need. And also it depends on whether you'll need many multiple operations. For myself, I probably wouldn't bother with the extension unless I needed to do more than 3 operations in an image.
Also, keep in mind that it doesn't save a lot of time to use the multiple operations, because Inkscape actually still does them one at a time (as far as I know). It's just that you only have to select and click once. (Although it seems like I might have heard some discussion about making the operations happen simultaneously, so that it does save time....but I'm not sure if that was ever actually accomplished.)
Anyway, by using the path operations, you are actually cutting the paths to the proper size and shape, using the clipping path. So you would never need to export a JPG or import or align it. Well, not unless using the JPG provides some kind of advantage with engraving, as opposed to using the SVG itself. I don't use any kind of cutter or do that kind of work, so I'm not sure if there might be some advantage that I'm not aware of.
If you do still need to re-align it, maybe you could use a couple of intersecting Guides to create something you could snap the JPG to, after you import it? Do you need info on snapping and/or guides?