[ @sanctiondecision ]
--- Thoughts ---
There's no exact solution as it depends on the condition (mini pc, tasks, specs, etc). The solid solution is to always get a proper conventional PC or Laptop. Remembering it is a Mini PC, you can't expect it to have a solid cooling or it has but under normal uses only (obviously not gaming, especially it's fanless). Having 47.2 - 51.1C is still relatively normal in general, but because the temp is gradually increasing, you should always pay attention to it, especially when the temp reaches 80-90C. Theoreticly, if you're using relatively new Motherboard, it has some throttling feature if the hardware reaches a really high temp, it will lower the frequency to compensate the temp, it is called "BD PROCHOT". I think you can do both; you can continue if the temp always sits under 80-90C, or you can optimize both Internal & External. I will assume that you're using Windows (since there're no emulation mentioned)
--- External ---
You can always buys some external fan, make sure that it has the strength to blow the heat out. Having an AC would help a little bit.
--- Internal ---
1) Since Windows is bloated, get some modded optimized Windows, like GG OS; this could help in decreasing amount of system tasks. You can also use some debloat script to remove unncecessary Windows Component.
2) You can use always use Throttle Stop. Make sure that BD Prochot is turned on and use Balanced - Powersave templates. You can go advance by doing under-volt with it to fix high-temp (Not Recommend if you're don't know what you're doing)
3) You can use Process Hacker. You can managed how many resources the app should use. You can play with Priority, I/O Priority (related to Read/Write in-app files) and Affinity (how many CPU that the app should use). Caution: it may cause lags for your game or even crashes.