I need to run 1080p 240hz so I think HDMI won’t work
I don't think you understand how multiple monitors work. Three 1080 monitor is not 1080p resolution really, they are 5760x1080, which will kill any card when running that resolution, never mind trying to run it at 240hz.
Adding a USB C video card with Display Port will be a lot slower than the speed of your video card HDMI port. What you want to do won't happen even with a top of the line video card. You may get to 3 displays at 60hz pretty well. Have you see any of the pro setups use 3 monitors for gaming? If you want to have good results, get a single 27" 1440p display.