Country domains
A .fr or .de domain sends a clear geographic signal, but each domain has to earn its own links and maintenance multiplies. It fits when each country has its own team, catalog or brand.
Subfolders or subdomains
Subfolders (/en/, /fr/) keep everything on one domain and are usually the easiest to maintain. A subdomain makes sense when that version runs on a different platform or server.
An example you can check
Nexuradigital.es itself is published in 32 languages, each in its own subfolder with translated URLs, reciprocal hreflang with x-default, one sitemap per language and right-to-left pages in Arabic and Hebrew. You can see it in its source code.