2 Wordpress sites in 2 languages on same domain, best option?

Need advice on what is the best option for my setup from SEO perspective?

I have a domain name "region".com The "region" is billingual and I would like to setup 2 wordpress local directories in 2 different languages on this domain. What is the best option?
1. subdomain like eng."region".com and es."region".com
2. the other option "region".com/en and "region".com/es

The contents of both sites will be different. What is the best option from SEO perspective or both are incorrect and should be done another way?

It doesn`t really matter. If you take advice from Neil Patel, he says multi-language site should have subfolder structure /lang. Matt Cutts says subdomains are treated the same as the main domain and google is smart enough to figure out your site structure.

I usually go for the folder structure /lang but I also have blogs on subdomains and they perform well enough. So it`s entirely up to you I`d say.

If you’re going to use multiple languages and countries, I recommend subdirectories.

1st option is a good idea if your content is about different topics. However, each site won't benefit much from others backlinks.

2nd option is better but only if you have similar content(must be in the same niche), otherwise it may be counterproductive - google will start seeing you as general site rather than authority in your niche