The good news is that there are lots of things to try!
Is there a particular reason you prefer constant bitrate over average bitrate or VBR? YouTube will accept your video regardless of which method you use, so the choice boils down to the quality-vs-size tradeoff you’re willing to make for your local file. VBR will often retain the highest quality while being the smallest file size.
If you keep constant bitrate, a 200M bitrate could be overkill considering your inputs are only 100M. I get that you want to make sure no data is thrown away due to bitrate limitations, but double bitrate is a huge buffer.
If you really don’t want to use VBR, would you be open to average bitrate instead? Unless your goal is direct streaming (like from an FTP server) or physical media like Blu-ray that needs the buffer, constant bitrate will probably cause more problems than it solves.
Have you done a sample render with both one-pass and two-pass to see if the analysis pass is really gaining you anything? I do all of my exports with one-pass VBR at 68% quality and am happy with the results. Keep in mind that the purpose of the analysis pass is to figure out where the best places are to throw away data in the event that the output bitrate isn’t high enough to hold everything. In your case, your output bitrate is double the input bitrate, meaning data never needs to be thrown away, meaning the results of the analysis pass will never be used, and the time spent on analysis was wasted. (“Never” is a bit absolutist, but you get the idea.)
On the YouTube preset > Advanced > Other tab, there is a line that says
preset=fast which you could change to
preset=veryfast if you want a speed boost. Your output resolution is so high that I doubt anybody could visually tell a difference between the two presets. Your video will be downscaled to fit even on 4K monitors, so the nuances between
veryfast will probably not be measurable at all. Unless, of course, this is 360 video that gets stretched, but even then, I doubt anyone can tell the difference.
Given that you have an RTX 2070 card, hardware acceleration could be a legitimate option for you and would be worth experimentation.
Curious to hear about your results.