Which lens are you using?
I’ve found I have more adjusting for different lenses with the fiber compared to the co2.
I have a couple of tiles painted up with the acrylic/TiO2/water mixture…
There is a video by Laser Everything on photo engraving.
It is a great video that will show you how to set and get the best dpi possible for any laser with any material. It is well laid out with good graphics on what exactly is happening. It also covers the use of dot width correction, explained by the Lightburn developer… Simple touch of magic, you will want to use it…
I assume you do a lot of woodworking 
Hope you know a fiber doesn’t really work on natural materials, like wood… it also goes through glass and acrylic with no effect. These materials are pretty much not usable with a fiber.
Fiber lasers are generally pulse lasers compared to co2 and most led that are continuous wave (CW). The frequency of a fiber is 10X that of a co2, even though both are in the IR spectrum.
Not woodworking, but this is a trick setup for a fiber laser making flexible and Kirigami circuit boards…
