This seems hard. When would I use this? Consider OBS if you want to put graphics into your video live. Maybe you run webinars, or want branded graphics in your recordings - this can be done live. The nice part is you don't have to add it in post-production, and can record directly in OBS.
What does this sorcery cost? It's free.
How do I show people my video after recording with OBS? I've just got a video file now. You'll have to upload it somewhere, a service to host the video for you. I usually use Loom since it gives me simple editing functionality, and the player has captions.