I've never used a flower nail while baking because there is nasty glue leaking out of the joint between the top and the spike on all the ones I've ever seen. Ew.
I bake at 325 and never need to level anything.
The Ateco heat core nails are very nice, because there is no glue, they don't rust, and they are perfectly flat on the bottom. I poke them up through the parchment paper lining the bottom of the pan, so the flat part is outside of the paper, and the nails are very easy to remove.