I am making boxes using chipboard. Tutorial I watched states using Z Offset=1 is good for setting?
IMO, you want a well-focused beam to reduce charring around the edges of the cut. Which works just fine:
A slightly defocused beam can come in handy for engraving, but not for cutting.
Running a focus test will give you some confidence in having the proper focus. LightBurn has a focus test generator, but a simple ramp test eliminates a lot of hocus-pocus with the Z axis settings.