There are a few options besides flythroughs and screenshots. You can package the final product and ship it in these formats: PC game (best graphics, plus VR support), iOS or Android mobile game (lower graphics), or a “HTML5” web build, which is the mobile quality with a large download size considering its temporary life. Other options that I haven’t tried include TeamViewer (or other) remote access to the game hosted on your computer, or making a custom server thingy that hosts the game and streams it to the client whenever they like.