Add options in SharePoint :
- as Create a new site
- add users in groups
Also include an option to create a site from a template
Agreed. Need functions for creating new subsite, new sitecollections, new subsites based on templates. Breaking permissions, etc.
Looks like this is exactly what you need:
Create site by custom template and grant permissions
This article explains how to use Plumsail SharePoint connector, which is a part of Plumsail Actions (third party set of connectors for Microsoft Flow with a fair price).
This is also listed here: https://powerusers.microsoft.com/t5/Building-Flows/SharePoint-create-a-site/m-p/7438/highlight/false...