Okay i lied i have a couple of questions

1.) Whats the important difference between a top swing and a bottom swing derailer (front)?

2.) What role does the cage size play on rear derailers?

Im sure i have some other questions. Its been 7 years that i have been out of the mountain biking scene so its like damn all this cool **** now Thanks!

The top/bottom swing is dependant on your cable routing, either across your top-tube and down your seat tube or down your down tube around your bottom brackett and up.

Regarding the cage size is dependant on your cassette gear range. If your biggest cog is a 28 you can get a short cage, if it's in the 34 range you need a long cage.
A larger cog will require more chain to get proper "wrap", if you have a longer chain, you need a longer cage to "take up" the extra length.

L8R

ah sweet, thanks just making sure im ordering the right parts for my build. thanks again