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As said above, great question though.

Hi Roman, Ok great, you're at least also of the opinion that bigger sites will need an actual implementation. I want to make sure to at least mention these articles too, to not give people the idea that they should all go ahead to implement it through GTM, as it's still not a recommended way to go: https://www.upbuild.io/blog/dont-use-gtm-for-structured-data/ http://www.thesempost.com/google-dont-rely-google-tag-manager-structured-data/ https://www.seroundtable.com/google-google-tag-manager-seo-24984.html (see the Tweets mentioned in this article, it's based on John Muellers reply to my Tweet about all the down sides of implementing GTM for structured data).

I agree with Nigel and Google. You will be spliting link juice between two domains rather than building a single domain using langauge subfolders. The language of the page should be documented in the html tag. https://www.w3.org/International/questions/qa-html-language-declarations This is the way to go.

Hey Trazo--yes, you'll need to add the different variations of your domains to GSC. You should create separate properties for these URLs, then make a set of them (https://support.google.com/webmasters/answer/6338828?hl=en). In order to indicate to Google the primary URLs (www vs non-www), you'll need each url to be set up as a property. As for your SSL question, are you serving both SSL and non-SSL URLs on your domain? If you're not, and all the URLs on your site are SSL, you should make sure any non-SSL url counterparts are forwarding to the correct SSL version.