I can assure you that all the mods that or included in the current version of STEP have been tested and all work very nicely together and as for the textures alone a good thing to look at is Texture Pack combiner (
http://skyrim.nexusmods.com/mods/20801) the creator of the TPC has put alot of work checking out alot of the best textures throughout the nexus and has created a bat file to combine most of the best textures