I use Display under the settings menu, in the drop down it should offer choices, down to at least 800X600. I have not seen options to change the refresh rate however.
If you have such as Nvidia card, with propritary drivers, then it is in the Nvidia Control Panel instead. The Noveau free drivers, do just use the Display icon.
Antergos does install the propriatery driver as part of the CNCHI installation, has a slider switch which is a plus since factory drivers offer 2D and 3D acceleration modes. Even cooler is like Windows that you can have dual displays with your choice of resolution, and whether or not to mirror or stretch the displays and to swap them around as desired.
Another cool thing as that you can have seperate wallpaper on each display, and it also changes the wallpaper at random again on each display.