Be aware that "5 days early" is mostly advertising hype.
You have to understand how ACH bank transfers work. The sending bank (IRS, company payroll, etc) sends an advance notice of the deposit, 1-2 business days before the actual deposit. Then the actual deposit is confirmed. The receiving bank may wait up to 2 more days before allowing you access to the funds (depending on their own policies) to make sure the deposits clear ("settle") -- in other words, to make sure the sender really has the funds.
That means that in a worst case scenario, your employer'r payroll company will send notice of the pay deposit on Wednesday or Thursday, confirm it on Friday, and some banks would hold the funds until Monday. So if Credit Karma gives you access as soon as they get the advance notice, they can call it "5 days early." But the reality depends on the payer and your current bank's policy on deposits.
For me, if the payroll advance notice is Wednesday, I get access to the funds about 3am Friday morning, so about 36 hours after the advance notice. Credit Karma might give me access 36 hours early, but not 5 days early. If your payroll is Friday and the payroll company sends advance notice Wednesday, there's no way any bank can give you access earlier than the advance notice.
