Prevent Cpu throttle on Battery

I may set it at 25% instead of 5% that it's defaulted to while plugged in.

Setting the CPU minimum to something higher will not make any difference to performance, only increases power consumption/heat when the CPU does not have to work hard.
The title of the thread is wrong to call it throttling. The CPU is designed to increase up to the turbo max when demands are made on the CPU.

" I'm assuming setting it at 100% will make the CPU run at 2.8 GHz constantly"
Not on my Laptop.
The nominal clock is 2.5 GHz, however the turbo range or speed stepping ranges from 800 MHz to 3.1 GHz.
On the so-called "Best performance" setting the CPU has a 2.5 GHz idle frequency/min, but it still turbos up to 3.1 GHz when required.
The next setting down "Better performance" has the full stepping range from 800 MHz to 3.1 GHz.
On testing this with something taxing the CPU, "Better performance" setting is just as good as "Best" but with less power consumption between tasks.

The tinkering with settings by modding the Registry is pointless.

The Power Plans indicated are no more on the latest iteration of Windows 10 anyway.

"I may set it at 25% instead of 5% that it's defaulted to while plugged in. "

I doubt if that will do anything, it depends on the stepping range of the CPU clock allowed for your particular CPU. as you can see with mine it won't make a hoot of a difference. If it is set to 5% nothing happens it is still 800 MHz minimum(26%).

How do I find out the speed steps for my CPU (Xeon E-2276M)?