Whats the difference between RGB32 and YUY2?

Are there any disavantages/avantages as far as quality goes when encoding with YUY2 or RGB32?

Whenever I convert from RGB to YUY2 the video is a little lighter or the dark levels are reduced.
How can get I get the YUY2 video with the same dark levels like the RGB32 video with avisynth?

Why is it that some avisynth filter dont work with RGB32 videos?

Is it possible to IVTC a RGB32 video with avisynth? If so can someone show me how? (Because decomb.dll only works with YUY2 videos)

Last one....
When encoding do I choose Luminance Level 16-235 or 0-255? Whats the difference.


Thanks