Explain the Resolution to Me....

I have been having some trouble getting anything close to the quality out of this X4 that I got for Christmas, mainly it looks like low resolution. I have been comparing my videos to others, and I have a few questions.

A benchmark, the Hero3 in bright sun: https://youtu.be/-5US2gV-pEo?si=wdnKpYCb9vlMmBxD
The Hero3 in lighting much like what I got in the next two videos: https://youtu.be/oKw96IuPJcU?si=LHZJlnh98E7iJ85S

My first video with the X4 -- I think I know some of what is wrong here, but maybe you can help me understand why it just looks pretty crap: https://youtu.be/_l_-Mw_tk5A?si=hqAlXm-iQS9nl9k8

My latest video with the X4, not full sun, but better light than the flight video: https://youtu.be/E0JtH8qygbM

A benchmark with an X3 (not mine, but with some slightly less than full sun lighting in several spots, and set up in the way that I have/will set my X4. An excellent quality video: https://youtu.be/Ctjm0aBeJd0?si=k_Z8LuVadzXkeb-A

So I want to know what you think is going on with the low quality I'm getting. But also, I have a question about the difference between my X4 and his X3 video. They are both at 4k.... so I had thought that the X3 would end up rendering in HD, essentially for each of the two lenses, so to speak. He is at 2160 4k, but my X4, shot in 8K, will only render in 2160 4k. Yet his looks better even than my 8k.

In fact, when I upload a 5.7k video to YouTube, it tops out at only 1080, the same as the GoPro Hero3, but with less dynamic range.... So what am I doing wrong?

Thanks!