As for the world being entirely seamless, as I already suspected, Nintendo is just good at hiding loading screens
https://www.eurogamer.net/behind-the-scenes-of-zelda-tears-of-the-kingdoms-ascend-ability
Link is actually transferred into a cube prism, while the environment around him disappears and reloads.
Elsewhere in the video, we see how the game loads when Link travels to the depths and into the sky.
For the former, the environment loads around Link as he falls through a tunnel. Once in The Depths, Boundary Break was able to remove the lighting and effects to reveal the textured ceiling of the environment and see the area in full.
When up in the sky, meanwhile, Hyrule is visible at all times but taken the camera down reveals the land in lower detail.
It's not magic, but Nintendo does hide loading screens better than the average developer :) The load times after dying could be improved though. But I guess the change log can't be undone, so the world has to reload after death with the changelog from the last save game applied on a freshly loaded instance.
This is pretty cool though
https://www.eurogamer.net/simple-airbike-makes-travelling-in-zelda-tears-of-the-kingdom-a-breeze
Feels a bit like "if you give enough monkeys a typewriter, eventually you get another Shakespeare" but it's testament to the flexibility of the fuse system that people can stumble onto working things like this. Fiddly to put together so I doubt it was intended. Now where does the steering stick come from :)
I'm happy in the depths, haven't gone back up yet. The light roots heal gloom damage and I found some flower that does the same, so no reason to go back up yet. Pootling along with 4 hearts and using Bokoblin arms stuck to spears as weapons lol. Bomb flowers seem to work the best though.
Btw how does the difficulty ramp up? It's a nice balance atm, not too easy, not too hard. But will probably get harder the further I venture out from the initial camera quest area.