Proper HD export format in Sony Vegas Pro 13 for a decent video size? So I have decided to unite in a whole video everything I have of my child. I wanna render it in a sole .mp4 file with 1080p, good audio, etc. I want all that (1:50:00) in 2GB or 3GB, no more. I've seen videos accomplishing this smoothly, but everything I've tried so far ends in 9-12GB.

What I need to do to achieve it?

Thanks.
I assume you're using the Mainconcept AVC encoder. 3GB for a 1h50m video implies a bitrate of 3.7 mbps. That's the average bitrate you need. Set max bitrate to 5 mbps.

Now, usually I render in two passes. First pass is a high bitrate from Vegas  (20 mbps or more) and then encode with ffmpeg, which is a free command line tool.

Command would be

ffmpeg -i vegas.mp4 -crf 23 -movflags +faststart final.mp4


ffmpeg offers lot more variables to adjust but the above should be enough for most size adjustment. Usually a CRF value between 18-28 (lower is better but bigger) works.