trying to understand how to use domain mapping with multilingual

Hi,
i am trying to understand how to use domain mapping with multilingual in my multisite.
i need to created 2 blogs.
one is mysite.site.com
other is mysiten.site.com
now i have one domain that i want to map to: http://www.mydomain.com
so the mysite.site.com need to point to http://www.mydomain.com
and the mysiten.site.com need to point to http://www.mydomain.com/en/

the first question is how to make this work?

the second question is what the best multilingual plugin will do the work to make my life easier with domain mapping plugin?

from the list as i asked here:
https://premium.wpmudev.org/forums/topic/need-suggestion-for-multilingual-plugin-for-multisite