Yes, it would be easier to start that way rather than migrating down the road.
No, not the original files that are uploaded (which is why we recommend restricting maximum upload size in the settings). Discourse creates optimized images for displaying within posts (to cut down on loading time/bandwidth use), but a user can click on that image to view the full-size original.
If it’s absolutely necessary, we do have a script that could be run manually from the command line every now and then to trim down the size of the original images stored on the server