There was an explanation on why RAM usage by OS is fairly high but I can't find it right now. I'll try to recall what I have read.
The person said that from the start, OS-es are designed to take up as much ram as possible to utilize what you have paid for. Imagine you paid XX amount of money for 32GB of ram but the OS only takes (let's just say) 4GB of RAM. In a way, to you might look at it as "Hey look my device has so much RAM left. Glad I have bought so much RAM and it's future proof." but actually that's bad. You have your OS on your SSD but your RAM is small, so how? The computer is not able to store more data temporarily into the RAM and therefore, slowing down the booting of OS. At this point if this happens to you, you might say "eh I just upgraded to SSD why it is still slow?".
Now after booting up, why is it still taking so much RAM? OS logic = "When you need it, they have it instant/on the fly for you." Plus, the computer doesnt need to go to the SSD to file that particular file again and the SSD is free to do other things, maybe R/W some other data.
Oh yea, if other apps need more RAM, then the computer/OS will know to "throw" which files that are in the RAM and create new RAM space for the app to launch/use.
This is what I've gathered/remembered. I'll try to find the article/video and put it here when I found it.

This is a starter.
SauceThanks bro for explanation. Yes I read somewhere on the net too on Mac OS ram usage. I just move from windows to macOS that’s why I’m not too sure of the ram usage in macOS. But then I still feel Microsoft apps is kind of lag in macOS compared to in boot camp. I find boot camp is more smooth. But then power not so efficient.