That's down to the software, which you can pick independent of hardware. There is an option on cloud.tacx.com (for paying users) to import a gpx file. I have ridden other users' routes, but not tried one of my own yet. Some have videos, but I just run in the background and watch iPlayer or similar. The downhill bits don't feel normal - more of a higher speed and a bit less resistance - but the gradient changes are otherwise good. Rouvy does something similar, but I didn't have a lot of success with that.
I have the original Flux, and it works well. Decent road 'feel' as these things go. The resistance and speed seems similar to actual roads when used with the TACX app - none of the Zwift +10kph more than outdoor speeds that I see on Strava. Maximum gradient is only 10% on that model, which is just about good enough, but I'd prefer more. I think the Flux2 does steeper gradients.