About speed problem , just press - to decrease emulatos's Clock speed , it will make your game slower. you have to adjust it until you feel the speed is "right".
But when you quit Chankast and launch it again , you have to readjust it cause emu's clock will back to 100% every time you exit the program.
If your game is too dark , why don't use color correction in your display properties to adjust bri,con,gamma even saturation and save it to profile.
To find appropriate level of bri,con . you can have chankast running in background and adjust the settings at the same time , Like this pic.
EDIT: I just read manny9158's Thread about Full screen tools , take a look at
http://www.emutalk.net/showthread.php?t=21264
You can preset emu's speed to use with specific game , so you don't have to adjust it everytime you quit chankast.