I would like to create several transcoding presets in Adobe Encore 1.5. The program comes with the limited number of presets, and I just realized that I can create custom ones.

Do transcoding parameters correlate between each other?
Is there a site or guide for creating valid transcoding presets?
For example, what is the correct Field Order or GOP Setting for different bit rates? If the Bit Rate of 7.5 has Field Order - Lower and GOP Setting of M Frame - 3 and N Frame - 15, should it be different for Bit Rate of 5?