Yes, when you import images to Photos it copies them into the database in the default configuration. If you're worried about space then the obvious solution is to delete the files in your folder system. Or move them to another disk as a basic back up.
You can also import the images in referenced mode. That means that Photos will not copy the images, but only maintain a link to them in the current location. Do not do this. Photos does not have the tools to manage referenced images. Importing and deleting are multiple step procedures. Any change in the path to file is tedious and difficult to repair. You're just storing up trouble for yourself.
As for the Import -> Edit -> Export dance, it's a bit absurd. Photos is a parametic editor, designed for a non-destructive workflow. It's also a manager for your photo media. This dance defeats the two core qualities of Photos, and if you really just want to destructive edit, then use a pixel editor and ignore Photos entirely. It's more simple.
BTW: Photos keeps the files in folders too.