Welcome to the forum!
Scaling (resizing) or zooming any raster image (PNG is a raster format, as is JPG or GIF, among others) will cause pixelation (distortion or blurring) of the image. It's because of the basic, inherent nature of raster images. And the ability to scale or zoom vector images without pixelation is one of the great benefits of vector graphics.
Vector and raster images each have their own specific uses, along with pros and cons. So the decision on whether to use raster or vector graphics should be one of the first decisions a user makes, before starting on their drawing.
If you set the DPI, in the Export PNG dialog, at 96.0, the image will come out exactly the size you intend. Changing the dpi will end up making the image larger or smaller, in Inkscape. (Although technically, as we were just discussing in another topic, while the image gets larger, the page size stays the same.) So if you intend to export to PNG in Inkscape, it's best to draw the image at the size you want in the end. If you expect the image to later be scaled or zoomed, it's probably better to use vector graphics.
(Also just a note. If you change the DPI in the Export PNG dialog, it will stay at that value, until you change it again. And I've found that just changing the value in the dialog doesn't reset it. I have to change it, and export a PNG with that value, to make the change stick.)
Does any of that help?
