I've fixed one part of the problem but not the entire problem. The reason there were no black lines was because the thickness of the lines were at 0 and brush sizes at 0 do not render. I found this out by doing some research and I came across this forum post which has made a slight improvement
https://github.com/opentoonz/opentoonz/issues/2895
As for the issue of it rendering in a lower quality than the animation, I still have this issue and have been trying to fix it all day today. I have tried to render this project about 15 times using all different file types in both 1920 by 1080 and 4K but it doesn't change anything.
Another strange thing about this is if I open the rendered file it is the same quality as the animation in opentoonz but if that file is placed into editing software or uploaded to YouTube the quality drastically declines and becomes pixelated.
I was thinking it could be because I'm working in Vector and I tried to change the levels but that didn't work. Honestly I've tried everything I can think of, really not sure now.
Here is the FX schematic and the output settings. The settings under MP4 are both set to 100