Yes, when you package your game for distribution, the cooker will make a compressed, smaller version of your project for people to play. As a dev, you have the editor with all your asset files, which of course are not packaged. A dev will always have a large source project to work on during production; that’s in general, nothing to do with Unreal 4- that’s how game development works.
Unfortunately, it’s hard for a dev to work efficiently if their workstation is slow, runs out of memory, etc. That’s why I suggested getting better hardware- for you to work easier and faster. Of course, this depends on your budget and goals.
Good luck with your game!