Use the Kill Switch option if you wish to take a break from trading. Use it to disable segment(s) you do not want to trade in. Kill Switch is applicable for a day only and all the segments are auto enabled the next day.
Freezing account, on the other hand, is to be used when you need to block trading in case you suspect a fraudulent transaction or any suspicious activity in your account or if your device is stolen. Your account remains frozen until you unfreeze it.