1. Driver is controlled by the OS at install.
2. EWS goes by the Browser UI language
Firefox = Hamburger menu > Options > Language
IE = Gear > Internet Options > General > Language
Chrome = 3 dots > Settings > Advanced > Languages
3. Panel UI is done via EWS or at the device
EWS > Properties > General Setup > Language & Keyboard
at device Device > Tools > Device Settings > General > Language & Keyboard Selection.