Katrin Weixel the difference between modern and classic team site is from this article :
"Modern" team sites are responsive by design and are much faster to create and use from an end user perspective. Following are some of the key benefits of the "modern" team sites:
- Designed to scale for any device natively without customizations for a fully responsive experience.
- Contain native news, quick links, and activity capabilities.
- Integrated with Office 365 groups.
- Significantly faster site creation compared to "classic" team sites.
- Include "modern" lists and libraries with support for Microsoft Flow and PowerApps.
- Contain "modern" page editing capabilities.
- Include an updated site contents page with additional insights on site usage.
And for me you can create juste One Communications site for The Home Page of your intranet and then migrated Classic Team site to Modern team site because it's very easier to use for your users. And do links from your Communication site to the New Modern team sites you have created.
And after in the 2018, you can use the hub site to do a modern intranet.