Watching different lectures on YouTube, the problem is some of them are recorded poorly with so much noise in the background. So I've been thinking about a way that lets me first put a gate plugin (REAPER's ReaGate) and then compression (REAPER's ReaComp) on Windows 10 master audio output, so that I can control the audio in real time. In short I'd like to be able to put NOISE GATE, COMPRESSION, DE-ESSING in real time on the master output of Windows 10 audio. Yes, Windows has some loudness and eq effect built in, but they don't give me the amount of control I'd like to have. I'm using the built in audio of my Asus P5K motherboard from 2008. I've installed Virtual Audio Cable, VB-CABLE and Jack Audio, and when I switch to them in Windows Sound Settings, none of them seem to output the sound of the video being played, but when I switch to Realtek HD Audio, the sound works. But those three programs won't output the sound. I don't know where the problem is.
You could try using a virtual "loopback" audio device as the system's default audio output for applications and redirect its audio into your DAW (Reaper) for processing.
(applications) ==> virtual sound card ==> DAW with plugins ==> real sound card output
That's how I do it in Mac with the SoundFlower virtual audio device. I have not tried this in Windows, but apparently there is similar virtual audio device software available: https://superuser.com/questions/117625/how-to-create-a-virtual-audio-device-and-stream-audio-input-with-it