The goal of the new W-4 is to get your tax refund/tax owed as close to zero as possible. It's always hard to advise on these without seeing everything, but this will help give you an idea of what you're doing.
If you prefer to be owed a refund at the end of the year or expect to make more money than your current job, here is one way to do that. You can still over-withhold from your paychecks by adding how much extra you want taken out each pay period on line 4(c).
If you prefer to owe money at the end of the year or expect your final income to be less than the income you're accounting for on the W-4, you can be more generous with your estimation of your itemized deductions on line 4(b) or conservative with your estimate of your non-W-2 income on line 4(a). For example if you are making 100k at this w2 job but know you have a loss of 20k on your business you can choose to put $20,000 as your amount of deduction on 4(b).
The IRS has a tax withholding estimator on their website that will help you get a pretty accurate result so that you don't have too much or too little income tax withheld: https://apps.irs.
If you need assistance with this, you can always email us at email@example.com