You're having the exact experience that I knew I'd have if I went with NR200. It's just big enough to be comfortable to work in and small compared to towers, but it's kind of pushing it for carry-on. You really gotta get to the 10L mark for it to be good. When I was going to college I had the Shuttle XPC style builds, which are usually around 15L. It definitely worked and fit, but practically speaking it's kind of questionable.
Even going down to 10L it's going to be really dense, the hardware is similar to bricks in density. I'm thinking that although it's possible to wrap it in clothes and put it in a typical carry-on, it could be potentially a better experience to make a perfectly fitted foam lined pelican case with the suitable accessories (telescoping handle? definitely want wheels) for the computer. Although some cheaper airlines try to limit you to a single carryon, as long as you're not trying to bring multiple very bulky items with you, i've never had problems. I'm still researching the pelican case angle... it might also just make more sense to make some sort of padded pouch that has handles and just leverage a normal carryon luggage by putting it in the bottom. The main idea here is that the PC will be so heavy youll want to have some system to help you manipulate it while you're in the security checkpoint, as it's a certainty that itll need to come out for bomb sniffing.
I have a ZX-1 incoming in the mail this week and will be setting up my 5950X and 3080 TUF in it. Hopefully it ends up fitting, I think it will but I worry about the PCIe cables.
I ordered the ZX-1 the first day I learned about it. I had been looking around for the perfect ITX case and just hadn't found the right one. It just ticks so many boxes. One thing I suspect though is that the GPU may end up slightly starved for air. I reckon it'd be easy to get custom side panels, and also to leave the side panels off during use. I wanted to make sure that the case would be robust enough for traveling and the design achieves this while being better looking than everything else.
Good luck!