YES!
WiFi - For one or two people phoning on the system from their home, wifi is fine.  You will want to be sure you're not sitting in a "dead spot" and pay attention to how many household members are also using the internet for streaming video, gaming, etc., but wifi will work.
If you are setting up a phonebank at a central location with a number of computers in an office, we recommend that you pay a little extra attention to setting up your network, so that all of the computers have a fast, reliable connection to the calling system.
Tablets - as long as your phoners are comfortable with the size of the screen, and your wifi is good, tablets can be used on the system.
Chromebooks, Windows computers, Macs - YES!