Hey Jessie -
For the questions around locales, I’d recommend this post - Impact of Different Languages/Locales - #2 by Liz_Frailey. It has a lot of context about the language profiles & their impact! In short, the locale will be set by a different field (‘locale’) rather than the Country/Region.
And yes, if all profiles are the same in the account, you can keep them as “en”, but adding GB to the countryRestrictions allows that country to be searchable on Answers maps.