Welcome to the forums. Here is a list of FreeSync monitors:
https://www.amd.com/en/products/freesync-monitors
I am going to be honest....I am not sure which one I would get. Here is why....
Let's look at this from a PC gaming perspective. If you get a monitor with a 144 Hz refresh, you are on your way to opening yourself up to a higher frame rate. Frame rate would be like looking at a flip book animation. The faster (higher number) rate, the smoother the animation will be. So, if you are using a system that gets 100+ FPS (we'll say 105 for sake of numbers), a slight dip (let's assume 10 FPS) into the 90s isn't really noticeable. If the same hit takes place on a 30 FPS, you will notice some stuttering, and freezes.
However, the resolution also comes into play. To have a higher FPS and a high resolution would require an above average card. So the resolution of the monitor you choose will impact frame rate.
Why I am not sure about which to choose is I am not too familiar with the GPU in the 1X. I would honestly say shoot for a 1080 monitor. I am not sure how many options are out there for a sub $400 monitor that has 144 Hz, with FreeSync.
Do you have any options already?