The quality of the conversion (text recognition) changes depending on the settings in color mode (B&W/Color/Gray) and image quality. What is the best setting?

The best parameters vary depending on the document types. Please try several different settings in color modes and resolutions.

[Reference]
OCR tends to achieve the best results when [Image quality] is set to "Better" or "Best" (Color) in the [Scanning] tab with the compression rate at "1" in the [Compression] tab.