There are people who don't like to cut panels off at all (gag manga/non-fiction manga), and there are people who cut off every panel (battle manga)
Do it the way that you like and suits your style!I'm fond of cutting it off. For an ordinary panel, you can cut it off, and for a talking scene, you can cut it offWhen you want to show the expanse of the space of a background, you can cut it offTo each his own!