Retirement tax questions

After further reflection on the extra tax added to the joint tax return for my daughter and her husband, it appears that TurboTax has added 6% of the excess contribution for 2021.  I am sure this is probably following tax code requirements.  What are the ramifications of not recharacterizing the two Roth IRAs for years going forward?  Will there be an excess tax added each year?  Will there be any other "penalties" added each year?  I am planning to file an extension for my daughter's return and then handle the excess contribution before the extended due date.  I am presuming if the Roth is recharacterized into a traditional the extra tax paid with the submission will be reversed and she and her husband will need to pay the tax on any gains from the inception of the IRA.  She can then decide whether to convert the new Traditional account back into an IRA.  I presume if done quickly there might not be any tax consequence other than a need to track a basis in each account that was converted.