Until a new UEFI is released with the latest SMU firmware and AGESA code its best not to overclock infract its best not to manually overclock at all the CPU part.

The CPU with Turbo Boost enabled and good cooling can boost all cores to 3.8GHz and even 3.9-4GHz on 1-2 cores depending on the power limits, the 2400G has Precision Boost 2.0 like the 2600X/2700X and mXFR/XFR2.0.

The problem is current UEFI's cant configure this features correctly resulting in GPU throttle, by overclocking you increase that throttle, take note the CPU will not allow for 3.9GHz on all cores with less than 1.445V for full stability, so its the same as keeping Turbo on, infact it will throttle more because of that 100MHz more on all cores.

From my testing best temporary GAMING performance until a new UEFI is release is achieved by going as high as you can on the memory frequency and leaveaing the CPU alone with Turbo disabled, for max gaming just overclock the iGPU with Ryzen Master to 1500MHz with 1.2V on SoC and GFX voltage, be careful when bumping the SoC voltage, dont go over 1.25V

If you want highest productivity performance just leave Turbo enabled.

If you want highest benchmark scores leave turbo enabled and just go manual on the CPU and set 3900MHz with 1.45V, but you need good colling (when overclocked to 3900-4000MHz TDP of the 2400G will jump to about ~125W from default of ~65W) 

You can even set 4000MHz with 1.45V, but again that will throttle the GPU part until a new UEFI

My 2400G can do 4150MHz with 1.45 on the CPU and 1650MHz with 1.25V on the GPU with the memory @ 3333MHz. I will gain all the performance from this in say CS-GO but it will throttle like every 5-10 seconds, making the game unplayable, so I still have better performance with everything stock and Turbo disabled, I just keep the memory at 3333MHz

What ASRock needs to do is update the UEFI's with latest AGESA and SMU firmware and add a normal entry for GPU frequency in AI Tweaker like all other manufacturers and not a HEX one hidden in /AMD CBS

Cheers, and have a nice day

One more thing: my setting for turning off core boost and GPU frequency do not save for somre reason. It just defaults to "auto" after reset. The only thing that stays is the CPU overlock and XMP profile. Any idea what the hell is happening? I have the latest BIOS updated to 4.60.

It has no positive effect, instead you will increase power draw, and shorten the lifespan of the chip.

And regarding Ryzen Power Plan, it has no effect on preformance, its the same as Ballanced/High Performance, because those two plans already are the same, in fact all power plans are the same on a desktop with no effect on performance

The 2200G/2400G has problems with the current AGESA code, you cannot fix the stuttering in games by locking the frequency, and its not the CPU part that throttles, its the GPU part, that drops to about 200-400MHz that causes the stuttering. Instead a temporary fix is to disable Core Performance Boost, this will lower the max cpu frequency to 3600 and max voltage to about 1.25V instead of 1.445V with turbo boost.

This will provide a somehow lower stutter rate but not fix it.

AMD released AGESA PinnaclePI 1.0.0.2a that should fix these issues, but ASRock still uses AGESA 1.0.0.1a in current UEFI's, they will release updated UEFI's this month or next month.

The true problem here is a badly implemented total socket power managment by AMD, when the CPU is under 100% load the GPU cannot also sustain 100%. In reallity it can but the AGESA code has a problem in the SMU code that makes the CPU think it has reached max allowed current draw so it will throttle the GPU part.

By turning off Turbo Boost you lower the CPU max voltage to 1.25V aprox. and that makes the the CPU think it has more headroom so the GPU will and can sustain longer periods of 100% clock and load without throttling, but it will still throttle but not that much as with Turbo Boost on. This is not a phisical problem, its just a bug in the code of the SMU/CPU

PS: Ryzen 2xxx can switch very fast between P-States so fixing the frequency is a bad mistake and under no circumstances should it be done.