export without rendering

Filesize = bitrate x duration.

Post screenshot export settings.

If your disk is filling up quickly, it means you need a bigger one.

File size has to do with codecs, compression and data rate. You have to make sure you're compariing apples to apples. The effects, titles, etc., you add to your movie has no effect on the size of your output video.

It's rare that your output file will be exactly the same size as your input file.

Beyond that it's hard to say without knowing all of the detailed specs of your source video or even what device recorded your original video. Premiere Elements can reduce the data rate of your files and quality if you really want smaller files. But in most cases the files it produces are the right balance of quality and file size.

Where did your original files come from? What if, as an experiment, you take a five minute clip of your video and output a five minute movie from it? How large is your original file and how large is your finised movie?