Well, I experimented a little bit with sound options following Paul's remark. May be of interest to others trying to release videos themselves:
My research yielded that apparently there is no one stop shopping software that can generate videos with high quality sound compatible with audio software (though a lot of others have asked for it). My guess is that a) audio and video expertise is so highly spezialized and complex that any company focussing on one would be at loss trying to do the other as well and the computing power needed to render both audio and video recording simultaneously would make a single piece of software for both unattractive.
Whichever, here's what most people recommend and what I ended up doing: I recorded the sound just as usual w/ Cubase and my audio setup (exactly the same thing as when recording audio only) and exported the sound file. At the same time, I recorded the video with the low quality built-in microphone.
This yielded two files: A video file and a sound file. Using video processing software (in my case, Microsoft Video Maker), I added the sound file to the video and aligned it until the sound of the built-in micro and the "good" sound file completly overlapped. Then I muted the built in sound track and exported the entire thing as a new video which I then uploaded.
Here's an unlisted video (quick and dirty style) generated with this process:
I'm fairly satisfied with the result (at least w/ respect to the sound quality and video/audio synchronization). An additional bonus is that the sound file can also be used separately from the video. The workflow is more cumbersome compared to a desireable single recording, but the entire process was surprisingly simple and intuitive (I got done with the video in less than half an hour which included figuring out the workflow).
Edited by RAc, 06 April 2018 - 07:12 AM.