my payroll expense account does not match the amount of my w2's
It should be higher. Payroll includes not only gross wages but also can include employer share of 941/940 and state unemployment unless you specifically redirect these to taxes and/or insurance. Speaking of insurance, workers comp is insurance but could be rolled into gross payroll.
You can run a detail report of the payroll account to determine exactly what is pisted and when
They will rarely match. Your expenses include company paid taxes and other benefits that are not included in Box 1 or any other box.