This question is totally independent of AEM as a Cloud Service, the same approach should be applied when using a different AEM version as well.
The biggest concern here is to find the right content architecture. You might not only reuse the same components (and their settings), but also you might reuse content. You might check a blog post I have written some time back: https://cqdump.joerghoh.de/2017/11/13/creating-the-content-architecture-with-aem/
Best practice is to plan a bit ahead, so you can place the content of subdomain1.mycorp.com next to www.mycorp.com in the content tree, for example:
/content/mycorp/www.mycorp.com/...
/content/mycorp/subdomain1.mycorp.com/...
Here the subdomains are clearly separated, and you still have the chance to host multiple brands. Don't forget language and potentially country hierarchies when designing your content architecture.
And from there it shouldn't be problematic to allow reuse of components and templates.