Two sites, same content, different languages Duplicate Content

Hey guys,

I have a site with WPML and four languages on it: German, English, Russian and Latvian.

Now I want to split these into two sites with different URLs:
1st. German (without WPML for Performance matters) relevant for German Google search.
2nd. all other languages (with WPML or Polylang) relevant for Latvian Google search.

These two sites will have same/similar content but in other languages.

Now my questions: How do I avoid duplicate content? Maybe one of these opportunities:
1. Should I put canonical tags on the 2nd site referring to the German site? I’m afraid this will harm the 2nd sites performance. Or Doesn’t it matter as they rank on different Google Pages?

2. Can I somehow put Hreflang tags manually referring to the other sites, as I don’t have WPML on the German version?

3. Should I use Multisite with one WordPress installation? I actually wanted to avoid that as I thought it might harm the speed performance.

I’d really appreciate your help 🙂

Thank you!