You have to export copies, and you can specify the resolution in the export dialogue. But the easiest way to provide high-resolution copies for your client is to give them full-sized JPEG images. Changing the resolution number will have no impact on the quality or the resolution. If you want to send them low-resolution images, then resize them to something like 800 x 1200 pixels. Again, the number in the resolution box has no impact on the quality. But you will have to export the copies in two export operations because you can't export two different sizes at once. You don't have to wait for the one export process to finish before you start the other one.
I don't see the rest of the string on your question - and don't understand the context of your inquiry?
However, If I had a large volume of image originals that needed to be formatted a particular resolution and size I'd import that folder into LIGHTROOM.
and export them all to a specified size and resolution - all in one batch.
Let me know if this is helpful or if I'm not getting it.