The JJazzLab SoundFont is optimized for JJazzLab with a good trade-off between sound quality and ease of set up.
This free SoundFont contains 128 high-quality GM sounds plus some extra sounds. It also contains 14 XG-compatible drum kits.
Most Yamaha styles use the XG drum map, which defines more drum sounds than the GM drum map. If your output synth is not XG-compatible JJazzLab will make its best to make the style drums/percussion sound OK, but it may be not optimal.