Orca Slicer is a fork of Bambu Studio which is a fork of PruaSlicer which is a fork of Slic3r. I have used several slicers throughout my time printing and will probably continue to try other slicers, but Orca is my preferred slicer. The reason I settled on Orca Slicer is that it has a lot of built in print calibration tests that make getting the most out of each printer easy.
The development velocity on this project is great, so most shiny new features that come to other open source slicers also make their way to Orca quickly.
I usually run the calibration in this order after first calibrating the nozzle height on the printer itself:
They provide a detailed guide that has more advanced calibration here.