You can try the 720p 60fps, some say it is much better and it is smoother in rapid movement or turns.
I find the 1080p 30fps is best in most situations.
Youtube seems to work around the 30fps setting, or rather it won't run at more than that no matter what.
If using the 25fps settings for US TV that should work fine too.
I usually set the exposure to -0.3. In typical bright flying conditions lock the ISO on 100 rather than auto, or it can change during the flight giving inconsistent exposure..
Similarly the white balance left on auto will sometimes change when you'd rather it didn't - usually best set on 'sunny' but 'cloudy' might give a warmer look.
I wouldn't describe the video as 'grainy' but there is rather too much sharpening or unsharp mask applied.
If you have software which can sharpen in an adjustable way afterwards, you could try the soft setting for that too; only it is very soft indeed. I found the default middle setting was best as a rule, but sometimes apply a very slight blur afterwards which just smooths those harsh edges a bit.