Photoshop brush packs cover very different workflows. Ink, pencil, charcoal, dry-media and paint brushes are designed for continuous drawing, while smoke, cloud, grass, crack, splatter and texture brushes may behave more like stamps. A search for Photoshop brushes, watercolor brush, paint stroke brush, grunge brush, smoke brush or halftone brush can therefore lead to presets with completely different spacing and dynamics. Test the actual stroke before deciding whether a pack fits the project.
For illustration and lettering, pressure response is important. Shape Dynamics can control size variation, Transfer can control opacity or flow, and texture settings can make a digital stroke feel less uniform. A preset that looks natural with a pen tablet may behave differently with a mouse. Keep one clean test layer and adjust the brush settings for the input device rather than assuming the downloaded default is the only correct configuration.