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.
If you value the deep mechanics of .NET Script Framework, the precision of No Grass In Objects, and the assurance that your game will never be shattered by a random Tuesday Steam update, then downgrading to 1.5.97 and installing the legendary USSEP version 4.2.3 is the only logical path. Unofficial Skyrim Special Edition Patch 1.5.97
: Skyrim SE 1.5.97 (the "pre-AE" version favored by many for legacy SKSE mod compatibility). Patch Version : 4.2.5b. Without the USSEP, a heavily modded Skyrim is