Basically - not OBS (or any other real-time video encoding composite tool) questions
Those are YouTube specific questions. Updating your post title will probably get better advise/responses, or creating a new post with more useful title
Sorry, I don't stream to YouTube... but I'm guessing YT similar to other in allowing either a scheduled live stream, or an ad-hoc (manual) live stream
Then you have the basic issue of uploading a video (doesn't need to be livestreamed, though you could), and scheduling when it becomes visible/streams. If I'm recalling others conversation correctly, Generally, recording to local PC, and uploading to streaming platform will result in higher quality looking video than livestreaming
In the platform I use, Scheduling a live video event, will create a unique URL that can be shared in advance. there are plenty of YouTube guides on this, as well as their own documentation. This would all be done in the YT web interface.
The important thing to recognize is that you can create a video (using OBS or whatever) locally, upload and stream later.
Where livestreaming often comes into play is 2 scenarios
1. you don't want the delay of recording entire video, possibly editing, uploading, then streaming
2. you want an interactive experience (realize all streaming platforms will have carrying lag time from point of video being livestreamed to platform, until video re-encoded, distributed, and streamed out [can easily vary from impressively low 10 seconds, to a common 30 seconds, to longer depending on device and network receiver is on)
