No. That is what would cause the problem.
"Speakers/Headphones Realtek" IS your default device. You've get it set under "Desktop Audio".
Then, under Monitoring, you've got it set to Default. Which for you is "Speakers/Headphones Realtek".
So if, under Edit > Advanced Audio Properties, any source is set to monitor only OR monitor and output, those sources will echo, because they will be sent to the default device and captured, and then sent to the device again and captured, over and over.
You need to do one of the following:
1) Turn all devices in Advanced Audio Properties to "Output Only". You can't monitor on a device you are also capturing, and if you don't have a separate audio output to use for monitoring, then you can't monitor. If the default device is what Windows is using and what you are also using (say, the headphones you wear while streaming) then you should not need to use monitoring, you should just hear the default output anyway. Monitoring is useful for devices you are capturing that you could not otherwise hear (for instance, audio from a capture card connected to a camera or game console.)
2) Set monitoring to a separate device. If you have USB headphones or any other plug you can use, set the Monitor to that other device and use it for monitoring.
3). If you can't do either of these for any reasons, then what you actually need is 3rd party software to take over audio routing from Windows. This allows you to create a virtual audio device to use as your default, and then use that software for monitoring. For this most people use Voicemeeter, but be warned using this is more complicated than the above two options, although it does greatly increase control and flexibility.
https://obsproject.com/forum/resour...nagement-for-1-and-2-pc-streaming-setups.397/