Im rather new to the forums but I have some knowledge outside of assigning video settings that may help.
First I wanna show my understanding of the video settings for a bit of context: (yes I read the G-sync and various other monitor guides)
I like to view settings as a cascade from program/game to driver/GPU then to Monitor.
So you can sync the game output to a set amount in the game's frame limiter or framecap software.
Then changing the GPU settings you can use Vsync for frames that are to high or G-sync to smooth out frames that are to low.
Then obviously you have the Monitor settings for framerate and other settings.
Now, beyond these settings you have the physical hardware settings like MSI afterburner and BIOS settings.
Additionally thermals will affect framerate consistency because the GPU or CPU will downclock to compensate BUT,
Have you considered that boost clocks/powersavings would also be the blame for inconsistant frames?
To check/sort out your CPU you need to disable clock boost and power saving functions.
I don't know the exact setting name as motherboards can differ especially between intel and AMD.
Your looking for a setting called C-state, Global C-state, AMD CBS, Core Performance Boost, Power Supply Idle Control etc.
This is usually found in the advanced section of the BIOS. (Some BIOS's have a Ez menu, be sure to disable this to see all settings)
If your unsure which setting to change, send screenshots here and I can navigate you.
For GPU you can follow this guide to underclocking your GPU:
https://www.youtube.com/watch?v=kh1QsSCt4Xk
The reason why is because the default GPU clock will dynamically adjust to your voltage and frequency depending on your temperature,
But regardless of temperature the frequency will keep fluctuating which in turn fluctuates game FPS.
Also disable power save functions in windows.
Observations of DOTA:
I don't play the game but from checking out some gameplay the stutter maybe a case of the game is loaded in that view then when you move to a different part of the map it tries to load more things which can cause FPS dips/stutters.
So if you had say a power save setting enabled for your CPU for example, the view you loaded into has completed, the load is reduced and then the C-state or power save kicks in, then when you move to a different view it suddenly asks the CPU to load the game agains while its in the lower power C-state causing the stutter.
There could also be a case of poor CPU resource management while playing the game but given Ryzen CPUs have a bunch of cores, I dont think that would be the case.
But yeah,
-Remove the boost clocking functions of your GPU and CPU to stabalise framerate.
-Disable C-state power save functions in the BIOS of your CPU to prevent stutters.