Though I realize now, you're simply asking for a device for recording and writing
If I wanted to keep it simple I'd just use https://screenapp.io/#/ and a paint program (correction, The bright side of mathematics, which looks a lot like your blackboard video, is probably JUST using onenote) to have the same effect as the video you posted. Maybe edit it a bit in adobe and than get it up on youtube as well. I could make an example if I can figure out how to upload to Youtube, if you would want that?
These are mostly "visual aid" on some subjects in math and economics, which I found to be very good for understanding subjects quickly
https://www.youtube.com/channel/UCYO_ja ... V4b17AJtAw 3blue1brown
https://www.youtube.com/channel/UCoxcjq ... p3uz647V5A Numberphile
https://www.youtube.com/channel/UCdwo4k ... _-WS7Cazqg The bright side of mathematics
https://www.youtube.com/channel/UCZ4AMr ... X6nsU8-rPg Economics explained
https://www.youtube.com/channel/UCKzJFd ... r_BkTfN3uQ Primer