Camtasia Studio video files are too big
The filesize is determined by many factors. First, check your resolution. If you're exporting in 4k or 6k, your filesize might not be strange at all. Next, the framerate plays a big part in filesizes aswell. Check if you're exporting in 30fps (for most web-videos), 25fps (for tv) or 24fps (for cinema). It might just be that you are using something like 60 or 120fps, which bloats the file. Next up is the codec and container you are using. You mentioned trying the .avi and .mp4 container, but which codec were you using? For .mp4 files I recommend h.264 or h.265, which are the most common codecs for mp4.