Fan running at high speed almost never has anything to do with RAM. Just means your computer is getting hot. Fans may also pre-emptively be cranked up when your CPU (or sometimes GPU) is working close to full capacity. Given that Beelinks are small PCs their airflow in general is pretty lacking and so their fans have to be running pretty hard all the time. That being said overall your symptoms point more to a CPU or drive issue than it does a memory one. 16gb on a Windows machine unfortunately is pretty slim these days given how wasteful the OS is, so I'm sure the RAM update wouldn't hurt but I'm not sure it'd solve all the issues you're seeing.