Site moving and URL or domain change can be risky and niggling at times. There’s no certainty whether the site would perform exactly the same way on a different domain, as clarified by Google’s John Mueller on Twitter. According to John, there are many SEOs and webmasters who are well-versed with such site migrations and have the expertise in mitigating such risks effectively. There’s always a possibility for temporary fluctuations during migration and normally settles down after some time.
Always remember, there’s a checklist in Google scheme of things while domain change related to SEO and beyond. As long as you are sticking to a target and you’re not missing anything, you are on the right track. Things might turn complex that means fixing can be difficult if you miss something important. Generally, migration from HTTP to HTTPS stays quite simple and smooth. But whole site domain migrations are not always so easy, even URL structure changes.