You only need to check the Overclock box if you are planning to overclock your CPU. Most people with a 14900HX struggle to keep it cool when running at default clocks. Most laptops do not have the necessary cooling for overclocking.
Checking this box will throttle the CPU a little if the voltage gets too high. Given all the recent issues Intel is having with their CPUs degrading, likely due to high voltage, leaving V-Max checked might not be a bad idea.
do i have to change the power limit 4
You do not have to do anything. I prefer to set PL4 to a value of 0. If the present setting your computer is using is not causing any throttling then you can leave it as is. You only need to change a setting if you have a specific problem you are trying to solve.
checking the MMIO lock could mess with the razer synapse performance options
That is likely true. If you are using Razer Synapse to manage performance then do not check MMIO Lock.
Checking the mV Boost box and setting that to approximately 150 can help reduce light load crashes when undervolting. The CPU Core, P Cache and E Cache do not all need to be set to the same undervolt value. It is OK if they are set equally but you can also adjust these individually however you like. Usually setting the core equal to the P cache or a little higher works best.
Other users with 14900HX CPUs have recently posted their ThrottleStop settings that they are using. Scroll down a page or two in the ThrottleStop forum and you should be able to find some additional information.