Can Firefox and Chrome browsers execute scripts simultaneously, and if so, what should you pay attention to?
Yes, they can! Or even easier, you can use different Chrome profiles. Each profile can run Ui.Vision independently. What I just said applies to the Selenium IDE-style web automation commands like CLICK or TYPE.
You need to pay attention to the XClick or XType. These commands control the global mouse and keyboards. So if you use these commands, you can run only one macro at the same time, otherwise the macros might interfere with each other. That would be like two persons typing at the same time