401k rollover and Roth conversion

1) My wife did a 401K rollover from her old company to her Vanguard rollover IRA in April 2024. Would the amount from a 401k rollover to IRA be added to our AGI or taxable income? Also, is it okay for her to do a Roth IRA conversion in a same year?

2) I am 65-year-old and my wife is 70. We plan to do a Roth IRA conversion in 4th quarter of this year.  Should we make a conversion from her IRA account first?

3) How / when should I pay taxes to avoid any potential underpayment of tax penalty after Roth IRA conversion?

Thank you!