If I buy it on store, is it tied to only that store for exchange it? or is it ok with any apple store in any states?
Are you are looking for Sumsung SSD and Screen? I don't think they will exchange it for you! Only if there's a problem with your macbook then they will fix but if you want to exchange I can almost 100% guarantee they will not honor exchange!
You can still exchange within the first 14 days... It wont be until after the 14 days, it will become harder to exchange for any reason...