It's possible it's not your Photoshop settings that are the problem here, but the settings on your tablet. If you're on Windows, check the "Pen and Windows Ink" settings, and see if "press and hold" is set to something. It could also be a setting in your Wacom Tablet Settings app. Sometimes the wacom tablet sets pressing and holding to do the equivalent of a right click, or bring up a menu (which is usually set to the buttons).