Managing Image Size Before and After Upload

I am new to WP and am having some issues understanding how to properly upload images and use them. I used Photoshop to create a PNG file 1500px W x 750px H. I created the image this size because I was under the impression that this would be the size I needed for a header slide to cover the whole screen on my home page. I am using the X Theme and LayerSliderWP and when I looked at their Demo slide image in the Media Library it was 2498px W x 272px H. I was thinking that the image might be narrower and and a bit taller than the LayerSliderWP demo slide.

When I uploaded my file the image was now 1200px W x 600px in Media Library, so I checked the media settings and found that the Large file setting was 1024px W x 1024px H. WordPress didn’t appear to crop image to fit the maximum large file size and I’m not sure if it was suppose to or not.

I selected my image in LayerSliderWP and to my surprise the image was now HUGE! I can tell you how large. Maybe four or five times the size it was suppose to be. I have tried changing the size of the original photoshop image to make it smaller, but no matter what I do I cannot seem to control the image size. Whatever image size I upload, see in LayerSliderWp bears no relationship to the original image size in Photoshop. I tried jpg files as well to no avail.

I realize I must be missing some toggle switch or size input setting, but I have looked everywhere and cannot find the cause.

Thank you in advance.