If it is a store that specializes in monitors then they will have multiple tests to show you.
but the simplest way you can check for dead pixels is getting and all white and then an all black wallpaper and check for either black dots or white dots.
as for BLB, you can see that with a black background, the more uniform the color is the better. BLB will show a orange tint near the edges of the screen (typically the corners)
if the glow is kind of white, grayish and changes according to the angle you look at it, then it is IPS glow. (something you can't change with IPS screens, it is not a defect).