They are both good laptop brands and you don't buy laptop by "which company is better" but what hardware is inside the laptop. amd is not better than nvidia but it all depends on which gpu is inside the laptop really. You can't say AMD is better than nvidia before you compare 2 gpu models. If you upgrade RAM you will improve you pc's physical memory not the cpu speed itself, so no you won't upgrade your cpu with that but you will improve your pc's overall speed.
Give me your $ budget and I can give you a laptop you should buy for the money