I’d err on the larger side for a disk. Assuming 1000 hours at 60fps, 1080p, serviceable bitrates I’d get an 16-18TB disk to start.
As to watchable that depends on how good your eyes are and the exact content.
I really hope you plan on naming these files descriptively or having a document that has tags and lists info for videos for easy searching as future you may not want to sift through hundreds of hours to find something.
The term you’re looking for is “bluray authoring”.
Search for that. Industry tends to use Scenarist but it would be too expensive for an individual and they probably wouldn’t sell to you anyways. There are semi-pro tools, most paid, some hundreds of Euros.
Edit: here’s a list of some of the better ones with prices: https://www.videohelp.com/software/sections/authoring-bd-hd-dvd