No. You do not need to set up a dedicated English booth unless you actually have the English booth [United Nations style] in the event.
Each booth for example French, German etc. will be able to hear each other in ICP and communicate regardless of what direction they interpret into.
You specify the “relay” language in the event settings just for information purposes.
However if you do have the United Nations English booth, definitely set up a separate booth for them. In the chart there is a dedicated group to send messages to the English booth [if it is configured].