I want to ask if is there a way to render them two times with same quality.
So you have raw footage and you want to edit then upload it?
In that case, rendering the same video twice is a tedious process and you should be able to edit the video directly. That is because processing the same footage twice may degrade the quality much more than bringing down the size and quality once.
If you have problems editing the .mp4 files because of their size, then it is possible to process the raw footage once and then use the processed footage.
The first render depends on the overall quality of the mp4's, which consists of resolution and bitrate as the two important things, then codec, which I will address later.
If you want to keep the same quality but a smaller file size, you will have to lower the bitrate to a point where the difference between the raw mp4 and the rendered file are the lowest in terms of frame details. This point (bitrate) is a preference and it depends on where you think is the best bitrate.
My ideal bitrate for a 1080p youtube video is 10-20 Mbps using H.264 codec. When you upload the video, youtube will process the video again to a bitrate of around 8-10 Mbps to save space.
The bitrate also depends on what contents of the video is. A video game recording might need a bigger bitrate rather than an animation or a recording of your monitor screen. The higher the bitrate of the raw mp4 files, the higher the bitrate of the processed video needs to be to contain all the details.
The next thing you need to find out is the codec of the original mp4. If it is a lossless (or uncompressed) file, then you can lower the file size to a much lower value by rendering to any of your preferred codecs.
If the video is encoded with an H.264 codec, which the most popular of the internet codecs, then you can either lower the bitrate using the same H.264 codec. Since H.264 is programmed to be efficient and use the most of the bitrate, lowering its bitrate will considerably reduce the quality. Alternatively, you can encode using the newer and more efficient H.265 or HEVC (High Efficiency Video Codec) which can hold higher quality with a lower bitrate. In some cases, I've seen H.265 videos have the same quality but have half the size of the same video but encoded in H.264. The only disadvantage of encoding in H.265 is since the encoder needs more arithmetical operations to compress the footage, the rendering takes longer than H.264, but not very much.
If you want, you can skip rendering the first time by editing the raw footage then rendering the video using H.265.
I recommend you to render using the 'MAGIX AVC/AAC MP4' format, more precisely the 'Internet HD' 1080p/720p (depending on your final resolution) and 25-29.97 fps (depending on the framerate of the original video). Then, if you want H.264, choose Mainconcept AVC, then either Variable or Constant bitrate (constant for a shorter render time). If you want H.265, choose NV Encoder (NV for Nvidia). NV Encoder only accepts a variable bitrate, because of the calculations between frame details that need to be done. You can choose your preferred bitrate in the 'average (bps)' space, then choose a higher bitrate in the 'maximum (bps)' space. This means that the bitrate is not locked to 10mbps, for example, but varies to a higher bitrate in the case that a frame contains more detail.
I also recommend you to experiment using a 10-second video clip and render multiple bitrates to see which values fit your footage best.
Let me know if you encounter any problems or have any other questions.