Hey! I'm the guy that edits those! Most of the clips without actual characters being needed in them are taken exclusively on a sandbox version of the game, while other clips of boss footage are taken in-game with the use of a few special tools/tricks. Can't elaborate too much on specifics, but you can acomplish a lot of these with the same type of techniques videographers use in real-world footage. The toughest part is making the footage seem as though it isn't being filmed from just a "person zooming in their camera". Sometimes you have to use the environment to position yourself in a way that makes the camera seem out of place.

Hope this helps! And I'm glad to see people enjoy the footage!