Effects on Kiddie Tax if my parents claim me this year VS if they don't.

Your "Kiddie Tax" won't change whether your parents claim you as a dependent on their return or you claim yourself on your own return.   

Who claims you as a dependent on their tax return (you or your parents), however, depends on who meets the requirements to claim you - not how claiming you would affect their tax situation. 

The Kiddie Tax is the tax levied on the portion of a child's unearned income that exceeds $2,200.

Here’s a step-by-step illustration of how a child with $15,000 of unearned income in 2020 would be taxed under the new law:

1. Regular tax rates apply to the first $2,200, which is exempt from the Kiddie Tax. The remaining $12,800 is subject to the Kiddie Tax.
2. The first $2,600 is taxed at 10%, leaving $10,200 to roll up to a higher rate.
3. $6,850 of the $10,200 is taxed at 24%, leaving $3,350.
4. The remaining $3,350 is taxed at 35%.

If your circumstances meet requirements, your parents may be able to report your "kiddie tax" income on their return, possibly saving you from having to file your own return. 

If your parents report your unearned income on their return, the first $2200 will be taxed at their marginal tax rate and the additional income may adversely affect their eligibility for certain income-sensitive tax credits. If you report your unearned income on your return, the first $2200 will be taxed at your marginal rate (potentially "0" depending on your other income and deductions).

See How do I report and pay the Kiddie Tax on my 2020 return? for your filing options and How do I report my child's investment income in 2020? for instructions.