I would not worry too much about the dpi at all.

You can change it, and it will not have any real effect on the quality unless you are also changing the pixel dimensions. On those programs that honour it, it will affect scaling on the screen.



You can install Paint.net and try for yourself:

1. Load some image and then choose Image/Resize.
2. Change only the resolution without touching pixel size, and you can see just the "Print size" will change.
3. Click OK, and nothing seems to have changed with the image on screen.