Right now, the Viva New Vegas 2019 modding guide suggests installing New Vegas Reloaded with (at least initially) just the updated shaders and memory management active. On average, would adding this basic NVR alone give my modded game better stability, worse, or neither? Same for performance/FPS?
I've never used NVR, so know that, but yes, I would say it can help with stability. The memory management system prevents textures from being duplicated in system memory if they are already in VRAM. So, it helps with out of memory crashes. Oblivion (don't know about NV) crashed at 2GB memory usage. Vegas being based on Oblivion's engine may have the same flaw.