Why is my NAI -> ZIT workflow with the Karras scheduler?

I have a T2I workflow with three samplers. First is 1024x1024 (NAI model / Euler A / Karras / 1.0 denoise). Second is another pass after a 1.5X latent upscale (same as above but 0.5 denoise). Images look good but not realistic. Third is a ZIT model focused on realism (with VAE = ae and CLIP = QWEN 3.4b). Just a single sample pass with 0.5 denoise. No loras. I did an XY plot with (Euler A, DPM++ SDE, DPM++ 2M) samplers crossed with (Simple, Karras, and DDIM-uniform) schedulers.