[GERGE]

One more thing about TypeGenius. Let's say that you raised weight slider 2 steps, you can't turn the type back to the original weight and sharpness by lowering two steps. You have to edit Kobo's config file under .kobo/Kobo/Kobo eReader.conf (if you are using Linux or OS X dot before the file or folder name means the file or the folder is hidden, I have no idea if they are also hidden in Windows, never used it) and remove sharpness and weight lines for the font you want to reset.

And a recommendation, before playing with weight, you should check optical sizes and the book styles of your typeface if there are any. You also have to reboot the device after installing different forms of the same typeface. Caption usually works well with eInk with its lessened details and high x-height.