You want your laser as tightly focused as possible. If there’s a reason to defocus it, I don’t know what it would be.
LaserEtch and Image2gcode are both raster-style software, meaning the laser burns the image line by line. The only exception to that is then you use LaserEtch to cut, but it’s limited to cutting the outside edge of the image, or the border of the image.
Choose the height you want to laser to be. I use something around 50mm. Put the laser at that height. If possible, place something matte black on the work surface, it makes it much easier to focus. Turn the laser on low power. Focus the beam as tightly as you can. Make a gage to set the laser height above the work surface each time (a piece of wood cut to the right height will work fine. Something like this:
If you want to do something like precision cutting wood or plastic or vinyl, you will need to learn how to use ESTLCAM or another CAM program, or the inkscape plugin.
BTW, in case no one has mentioned it – always wear laser goggles!