Looking for install instructions

Hello All,
I would like around 60 users to switch from O365 to nextcloud
I have email server setup and the domains are configured and emails work with Outlook/Thunderbird.

What I am looking for help/guide to setup

  1. multiple domains for nextcloud
  2. roundcube for webmail for the above domains
  3. api/script to addusers ( since that what i use to create email users, would be nice to have usermanagement done via cli/api )
  4. Caddy serving the domains
  5. everthing running on localnetwork with caddy handing domains/ips and forwarding to local containers

Is there someone else who may have gone through this kind of setup.

Apologies for the newbie questions.

Ok have nextcloud working and love it … now onto roundcube … have roundcube working as well separately with https via caddy wwould like the app working what did i miss …cheers