The initial screen size, title text and button labels can be configured in Terminal Settings.

Screen updates are sent to the browser through a WebSocket after some time of inactivity on the communication UART (called "Redraw Delay"). After an update is sent, at least a time of "Redraw Cooldown" must elapse before the next update can be sent. Those delays are used is to avoid burdening the server with tiny updates during a large screen repaint. If you experience issues (broken image due to dropped bytes), try adjusting those config options. It may also be useful to try different baud rates.