Use a manual oc. All core @ 5ghz should be easy with a decent cooler. Use static voltage at first and start with 1.25 volts. When it’s stable change it to dynamic vcore and a negative offset till vcore under load is the same as the static vcore. For me -0.1 vcore is stable with temps between 75-80 under full load.
Don’t think you can easily get higher though. Above 5ghz the 10900k needs alot more volts. So it’s harder to get it stable with good temps. 5.2 should be doable but my temps rise above 90 and vcore goes too high for my liking. You can always try ofcourse but expect lot’s of blue screens and high temperatures during the process.
Ps. The 5.3 ghz is probably the max boost clock the cpu can achieve on 2 cores max out of the box (i believe) but once temps are above 70 the cpu will go to 4.9 on all cores. 5.3 is barely achievable on most of the cpu’s. Even with sufficient cooling. It’s more a marketing thing then a real spec because in the real world these clocks are very uncommon. That’s why most people will use a 5ghz all core clock. And to be honest, you’re not going to notice the difference between 5 or 5.2 in msfs.