The Standard Optimized option is ideal for most images. Subsampling averages blocks of color data so that they can be stored in a smaller space. However, it leaves brightness, which the human eye is very sensitive to, untouched. Thus, it can provide a powerful means of enhancing compression without adversely affecting image quality. If you need more compression, you should try decreasing this number 5 points at a time, until you reach the ideal combination of quality and compression.
Every compression format has an occasional problem image.
The settings shown above will allow your JPG image to maintain it's high quality even if it contains text. The trick here is to turn off Subsampling. Although Subsampling works great with most photos, it fails miserable with the hard edges found in text. If you find that your image still has some problems in the area surrounding the text, try increasing the quality to 85 or 90. Once JPG quality gets higher than 90, you start getting a major increase in file size accompanied by a minimal improvement in quality.