Disclaimer: despite having "yiffymix' in the name, the model itself has nothing to do with yiffymix.
I personally use it with these settings:
CFG: 6-8
steps: 23-150
Size: 512 x 704 or 578 x 768 (then upscale it. Some of the example images here are upscaled.)
Sampler: DPM++ 2M Karras or Euler a
PS: Consider using bad-artist embedding or boring_e621 as well. it's optional to use bad-artist embedding and you can try other textual inversions as well. If you see this, don't be an idiot like me. the way to use bad artist embedding is by adding bad-artist instead of bad_artist and you'll see it doesn't nessesarily improve the quality of the result. Boring_e621 is overall more recommended.