Installation questions about composer and Aegir 3.x to Devshop migration

[socialnicheguru]

What does that mean that the site has to be in composer in DevShop?
In aegir /var/aegir/platforms/myplatform/html/sites is where the sites on “myplatform” live.
So mysite would be /var/aegir/platforms/myplatform/html/sites/mysite
Would I have to place myplatform in git?
Would I place mysite into a seperate git repository?
Would I have multiple sites in the sites folder of myplatform like in Aegir with

Devshop or is it one platform to one site? I was using opcache to cache the platform. That might not work

If I am currently using Aegir 3.x and want to switch over to DevShop, I would first make a clean devshop install. How would I import sites from aegir to devshop? is there documentation for that?