Your tax bracket isn't on your W2, it is determined on your tax return, based on your taxable income, so your AGI minus your deductions and exemptions. Also, our tax system is progressive, which mean that a portion of your taxable income is taxed at 10 %, the next portion is at 15%, the next portion at 25%, etc, like layers. This is why some talk about using traditional 401k or IRA when they are in the 25% bracket, to put the higher taxed layer of income above the bracket cutoff into a tax deferred account.
The withholdings on your W2 are calculated based on how you filled out your W4: MFJ or S, how many exemptions, any extra amounts to withhold. You can tweak your W4 to fit your details. My DH earns more than me, and we have kids and receive EITC and CTC and college credits, so we generally owe zero tax. DH claims 14 exemptions on his W4 to get his withholdings to zero fed and state, but we don't get to claim 14 exemptions on our tax return! Some people want more withheld if they have other circumstances that will make them owe more tax, a side gig or investment income or something else.
Head of household is generally for someone who is not married but has a dependent.