Red Baron II came out with just Direct Draw Graphics. The Fan base complained and Sierra came out with Red Baron 3D which fixed a number of flight modeling problems, but also created a better graphics look using 3dFX's Glide graphics cards, which meant you needed to own a VooDoo card in order to see the better graphics. However 3DFX was bought out by Nvidea soon and shut down the Glide Graphics.
Here is a PhotoBucket Album showing very similar shots of Direct Draw and Glide in an otherwise pure stock game:
http://s1121.photobucket.com/albums/l515/Wailwulf/RandomPicsStuff/Glide%20vs%20Direct%20Draw/ What the Glide wrappers do is make your computer create Glide Graphics with out a Glide Graphics Card.
The Glide Wrappers I recommend most (CJ Glide) is game specific. DGVooDoo should be able to work with other games as that is what it was created for.
To get the Glide to work, place the wrapper in the game folder, and then in Preferences, select Glide.
The Glide Wrappers will use you computer's resources. How much depends on your resolution, your computer, the Glide Wrapper itself, and magical spirits or demons :)
For example, in the WinXP days, most folk recomended DGVooDoo 1.4 to me for I had a Nvidia, but DGVoodoo gave me only 5 FPS (Where they were getting 25 to 80 FPS). I used OpenGL (Which everyone said was best for ATI cards) and that gave me 25 to 30 FPS.