configuration within vimrc

[rudrab]

Dear all,
I just heard about LTex today. I have installed coc-ltex for Vim.
My coc-lsp-setting is:

g:coc_user_config = {
      \ 'diagnostic.errorSign': '',
      \ 'diagnostic.warningSign': '',
      \ 'diagnostic.infoSign': '',
      \ 'languageserver': {
      \ 'latex': {
      \   'command': '/home/rudra/.config/coc/extensions/coc-texlab-data/texlab',
      \   'ignoredRootPaths': ['~'],
      \   'filetypes': ['tex', 'bib', 'plaintex', 'context'],
      \ },
      \ 'latex2': {
      \ 'command': 'coc-ltex',
      \ 'ltex.language': 'en-GB'
      \ },
      \ }
      \ }

As you can see, I want to you both texlab and ltex.
I am having the following problem:

1. I want to change the language from en-US to en-GB.
2. I also can not find the proper command .

Can you kindly advice me proper vimrc or any other file setup?