Yeah, it's a collection of mods. OpenMW is an engine modification. It does very little that's noticeable on its own.
A lot of this has been around for many years, like the herb picking alteration and the barrel opening animation and, well, most of it really. I don't have (or want) everything in the video, but I have a lot of it and have had those changes for the decade or so my current mod setup has been in place. (The only thing I change these days is updating Tamriel Rebuilt when they do)