The render settings you will apply differ depending on where you want to watch the movie later. For viewing it on a PC, pixel aspect ratio of 4:3 or 16:9(widescreen) and try to stay at 30 fps. But, for example, if the video source is PAL 25fps, leave it like that. A PC can play any aspect ratio and fps, but to get best results you will want to set the aspect ratio like the screen you'll play it on. If you take a 4:3 video and play it on a widescreen you'll get vertical letterboxing (the black bars). You can fit the size to the screen but stretching will occur. There is no perfect ratio, you'll have to find some compromise. I would also recomend to not resize the pixel size, especially increase. Source is 1440x900 and ur increasing the output video to 1680x105, thats not good.
There will always be quality loss after editing and rendering a video, so should always try to minimize that loss. It would be good to edit the video when its still a big raw uncompressed .avi file.
About the internet i have no idea. I know that youtube recommends.mp4 but you can get better results than that. Check these links, maybe it helps you.
http://vimeo.com/help/compressionhttp://forum.videohelp.com/