Hello, I have 1920x1080 @60Hz monitor and a AMD Radeon HD 6670.While running in 1080p I found text and other items to be to small to read; but when I changed the resolution to 1600x900 and then went to scaling options the Underscan/Overscan Slider was greyed out, making it impossible for me to force the display to take up the entire screen space. I'm using the 12.6 drivers
When using CCC lower your resolution from your native resolution, go back to CCC
and see if they aren't greyed out anymore. (When lower your resolution don't bring it back up until you've changed what you needed)
You're doing it wrong. Right click on your desktop, click "Screen resolution". Then select native resolution (1920x1080) and hit apply. Then, press on "Make text and other items larger or smaller". Lastly, select suitable size. If it's still too small, click on "Set custom text size (DPI)" on the left side, and enter percentages manually.