you can can nitrotech and cell-tech togethere because One is creatine other is protein.
Also, it dont really matter if ur stomach is empty or not if u take it after an
intense workout because your body uses up the protein and creatine so u need to restore it. But most likely after a workout, i dont think ur gonna have a full stomach.
Also, i think cell-tech is insanly over priced. but
nitro tech, you can get it for good price if you shop around even though is cost more then other protein. And thats because it only has whey isolates which cost more then other source of protein.