CK simulators, in fact all simulators are inaccurate for the most part. CK also provides VantageScore 3.0 scores which most lenders do not use when you apply for credit, CK is only good at alerting changes on your report, everything else should be taken with a grain of salt, especially approval odds and when they tell you you should have X number of cards so you would apply for more through their site, that's part of how they make money.
For FICO scoring (most lenders use some version of FICO scores), as long as individual cards are below 28.9% UTI and overall under 8.9% UTI, you're in a good place. You will also see the term "AZEO" a lot on here, it stands for All Zero Except One, meaning reporting $0 on all cards except one that you would report > $5, this will squeeze a few more points out of FICO. Personally I like to put everything on autopilot by letting all charges report to all cards naturally (7 cards) and set my autopay to pay full statement balance on due date, then you can administer AZEO the cycle before application to grab whatever points might be left on the table.
