12 words provide 128 bits of entropy.
24 words provide 256 bits of entropy.

It means 24 words are safer in security than 12 words, 256 bits of entropy compares to 128 bits of entropy.

Because Bitcoin private key provides 128 bits of entropy, 12 words for your seed phrase is enough.

Don't mix/ rearrange your word orders, it will complicate your recovery process and you have risk to lose your coins.

How to back up a seed phrase?
Bitcoin Q&A: Why is Seed Splitting a Bad Idea?