It depends. Let me give you a hypothetical with numbers to see if I understand your question and what you are looking to accomplish. You are basically saying you are anticipating a larger refund than what you want, and you wish to "reinvest" the refund (as it were) by reducing your withholdings next year (2020) in order to have more take-home pay, correct?
So, let's say that you earn 100,000/year, and your wife has a separate, smaller job earning 40K. Normally you have 5K (for instance) withheld for 401K. What you want to do is use the tax calculator to state that you are going to "elect" additional 401(k) withholdings to trick the system into lowering your income and therefore lower the tax withheld, even though in the end you actually are not going to increase the 401(k) deferral election. I don't believe this will get the effect you want, although it is a good way of looking at the tax effect of the rental loss.
You can use TaxCaster (click on link) to estimate the 2019 tax results. While there is no 2020 estimator tool as of now, the 2020 tax season, as it stands now, does not rate to be very different from 2019. (The brackets might be slightly more generous, and the standard deduction slightly larger). But the taxes will be very similar (unless Congress comes up with legislation...you know how that goes. We're not anticipating anything earthshattering in 2020, but you never know). If you use the estimator, set your withholdings to zero; you are only interested in how much tax you have to pay for the year. Subtract what is withheld from your wife's paycheck, and then you know how much tax liability you will have to cover.
Next step is to know what is your gross taxable pay per paycheck. If you are salaried, you should have consistent amounts deducted. Your taxable pay will be your gross pay minus 401(k) deferrals and pre-tax health insurance premiums. (Take into account any other pre-tax deductions you may have, such as an HSA funded through deferrals). Determine how much tax you must defer each pay period to reach your target. For instance, let's say your new adjusted tax (the target you want to hit after taking into account the rental loss) is $9800, and your wife anticipates $2,000 of withholdings from her paycheck. The total amount of Federal tax you need withheld from your paycheck is $7800 and you are paid bi-weekly, 26 weeks for the year. You would need your pay-period Federal withholding to total $300 biweekly. Using your taxable biweekly figures, you can look up the withholdings on the following chart: 2019 Publication 15 - Internal Revenue Service. (Click on link, and the biweekly withholding charts are located on pages 52-55. If your taxable periodic income is higher than the periodic amounts listed on the table, then you can go back to page 46 to determine the amount tax on higher income amounts per period). The goal is to find out which allowance amount gets you the closest to the target you want to achieve in connection with the withholding status (married, or married, but withhold at higher single rate) you choose to use.
The tax withholding estimator tool for the IRS does not do this for you, yet. The reason is because we are so close to the end of the calendar year and it doesn't allow you to project forward using 2020 dates. If you need to do this exercise now, you will have to use the reference above to make manual calculations. The IRS tool should be available early in 2020. If using the charts manually is too complicated, you may want to wait until early January to run the same exercise, and then adjust your withholdings accordingly.
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