I want to switch to Krita completely but I am not sure if it has the ability to use custom Photoshop brushes. (or does it not?)
It be good because there are certain custom artistic brushes that made by other people that I like to use. (ex. Kyle's ultimate brushes for Photoshop)

Krita can import some .abr photoshop brushes -- add them by going to the brush editor, select the predefined tab, and use the blue file icon button to add brush files to Krita.

However, Adobe never made the ABR file format public, so we're relying on reverse engineering brush files and we basically cannot load most of the advanced parameters, especially for newer versions of Photoshop. The last time Adobe published any information on file formats was for CS2...