Question about files resolution

If I save a 1080X1080 graphic as a  PNG, the file will be bigger than if I saved it as a JPEG.
So, when I saved the video, will this affected the final video weight?

That's utterly irrelevant for AE. It doesn't pass through streams/ binary data. All pixel data is expanded to uncompressed buffers and processed, then re-encoded and compressed for output. Otherwise it wouldn't make sense to allow a variety of formats to work together in AE and different output options to be used independently from the input format.

Mylenium

Resolution is the number of pixels. It is not PPI, there is no PPI in video or on the web. PPI only affects spring quality by determining how many pixels per inch are put on the printed page.

Compression is another thing. JPG files can be highly compressed and lose quality. MP4 video files can be highly compressed and the compression is lossy. MP4 files even predict in-between frames instead of saving all the pixels. You should never use MP4 files as a production format or for storing archival footage. It's lossy and the artifacts build up every time the file is resaved. 

PNG files are also Lossy, but the quality when compressed and when re-compressed is higher than it is for JPEG files. 

Then there is Bit Depth. JPG files are limited to 8-Bit so subtle gradients have problems with banding and the color data in a 16 or 32Bit AE project is lost forever. PNG files can have higher bit depth. I never save images I'm going to use again in an 8Bit format. It's the same with video. MP4, the standard H.264 distribution format, is only 8-bit. I never render a production master as an H.264 MP4. They are always 10-bit or better professional formats like ProRez. 

On the other hand, if you are publishing to YouTube, or Vimeo, or any other social media or streaming service, you are stuck with 8-bit files that the streaming service is going to re-compress to fit the available bandwidth of the viewer. The best option is to send them a file that matches their standards. Currently, that is an H.264 MP4 that matches their frame rate, frame size, and data rate recommendations. AE has many presets in the Media Encoder for all popular streaming services. If you send them a file that does not match their recommendations it will be compressed with a sledgehammer and not look as good as it would if you match their specifications. If you send to a broadcaster or cable company, or advertising agency, you must match their compression guidelines of the footage will be rejected.

There is a lot to learn. Until you fully understand video and image formats and compression technology, just stick with the presets for Comp Size and frame rate and for compression.