You need to read up on compression and CoDecs. MP4/ H.264 is compressed and there wil lalways be artifacts even at extreme data rates. That's just the way it is. You just normally do not notice these things on a TV, but may notice them on a computer. It's merely a matter of understanding compression to reduce them to a minimum and also a matter of using teh right tools. That is to say using AE is not ideal. Adobe Media Encoder is much better and there are tons of other tools out there. The rest is of no consequence - if you are looking for a magic button, then you will be disappointed to hear that it doesn't exist. It takes a lot of experience to get good results and optimize datarates.