New section with big differences

I am wondering about a certain thing.

My site is multilingual and there is similar content in each language with UX customization etc.

I would like to add an additional language section for one country in English. All my sections have different languages and here an exception because it is a country with a very high percentage of English speakers.

And my questions are as follows.

1. in the general version I try to have general language codes en, es, pt, I don't have en-US etc. so how to do in this case if it will be in English? en-and the code of that country? This is not a country with official/official English.

2. the site is about bookmakers. However, I know that the type of bookmakers it advertises have no chance of breaking through in this market so I would like to move away from the theme of the site and present the audience with a completely different type of bookmakers.
Will such a little departure from the theme not be bad? Still purely bookmaking theme, but a little different.

You can use just en instead of en_us au etc.. 2. I tried to change the subejct theme of content before with little success, for me it was hard.. my opinion is once you are set for a certain traffic type thats pretty much difficult to change.