Is there a certain ideal ratio of starter to flour? I have read 20-30% starter is ideal.

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Is there a certain ideal ratio of starter to flour? I have read 20-30% starter (bakers percentage) is ideal.

It depends on how strong your starter is and how much time you have.

I use 20% and the bulk rise takes about 3,5 our on 28 C.
It is then somewhere between 30 and 50% rise.
Perfect for ak proof in the fridge.