Skyrim Special Edition (SSE) version 1.5.97 , the compatible version of the Unofficial Skyrim Special Edition Patch (USSEP) is
This is the million-dollar question. If you are on Steam today, Skyrim will auto-update to 1.6.1170 or newer. So why go back? Unofficial Skyrim Special Edition Patch 1.5.97
Without the USSEP, a heavily modded Skyrim is a house of cards. With it, the game becomes stable, predictable, and playable. Bethesda has even acknowledged that many fixes in official updates were derived from the USSEP. Skyrim Special Edition (SSE) version 1