FIRST STEPS: If you are getting a lot of image noise/blur, first step MAY be to just install a fresh new version of ComfyUI Portable. Because your card may just need some install updates and work flawlessly with fp16/bf16, and do not need to force fp32.
1) Install new version of ComfyUI Portable
2) try running as-is first, without any special command line arguments
3) If image quality fixed itself, good!
4) If still noisy, then you can try the --fp32-unet
Beyond ComfyUI version 0.3.77, many users' ComfyUI no longer automatically uses FP32 for their model loading, so there was a noticeable increase in noise and quality for regular samplers. (It generated faster though) With Z Image Flowmatch this difference was much more dramatic as shown in the attached image.
If you want to use Flowmatch or use my Z Image high quality workflow: https://civitai.com/models/2226355/luneva-infinite-details-z-image-workflow
Then I suggest you compare your image results with these toggles to see what works best for you. (ram, vram, gen speed, quallity)
To set the toggle, edit your .bat file for launching ComfyUI, and add to the end: --fp32-unet
But how about using a ModelComputeDtype node instead to select? I tried this, and it gave me random memory problems, so my official recommendation is to use it at the command line level.