After some testing I found out that the ENB SSAO effect was the culprit in my case.
It was with a savegame that had a reproducable CTD at a specific spot that allowed me to do some testing after many many days of uninstalling, frustration, removing mods and (faulty?) textures, starting a fresh MO2 and so on. PRC ENB - Ultimate Immersion Preset (happend with several other presets, too)į4 and Mods (managed by MO2) installed on a secondary SSD Resolution 3440x1440 (with and without v-sync/fps limiter to 60 fps) I had random CTDs until yesterday and I want to share my solution.