Close all other open apps running on the laptop.
Are you running any anti-virus apps, cleaning/optimizer apps, or third party security software? If so, then uninstall them by following the developer's instructions since they are not needed on a Mac and usually causes more problems than they solve, plus they impact system performance. Also, turn off or disable any cloud based file syncing services or bittorrent apps which again will cause performance issues.
Try disconnecting all external devices as well in case one of them is causing a problem.
Check with Blizzard and Epic to see if there are any issues with these games on macOS (they usually have their own game forums where users will have more recent game related information than you will have on the Apple forums).