As in, channels where the presenter is laid back, calming, and the content is slower paced and chill. My go two examples are LGR for retro computer stuff, and Hainbach for experimental tape music.
Paul Harrell (RIP) for guns. His presentation style was a masterclass on how to convey information in a unbiased manner. Anyone who teaches anything to anyone should take notes.
He was entertaining without trying to be entertaining. If that makes sense? The man was demonstrating and testing hypotheses without giving two shits about likes and subscribes. Loved his dry humor, sometimes caught me off guard. “Wait! Did he really just say that?!”
Not Youtube, but on my streaming service there’s an America’s Test Kitchen channel and a “The Repair Shop” channel.
Michael MJD: Retro tech youtuber with a very calming voice and video style. Often installs operating systems on unusual devices.
Techmoan: Tech youtuber focused on old audio equipment.
Ashens: British Youtuber, who has been reviewing mostly poundshop tat and occasionally other random items in front of a brown sofa since 2006.
Geowizard: British Youtuber who does online Geography quizzes like Geoguessr and sometimes goes on adventures. The former part is probably more relevant to your question, though even his adventures have a nice, calm narration and music (that he wrote himself).
The Trek Planner: Finds interesting spots on Google Earth and hikes there, usually in the deserts of the Western US. Videos are usually more focused on the journey than the destination, so there will always be lots of nice views of nature. Honorable mention also to Desert Drifter, who did similar videos but unfortunately passed away recently.
Patrick Dickinson. Some old bloke from UK goes on Hikes and does wildcamps overnight.
Bernadette Banner - Historical handmade clothes and sewing tips
