[ovirt-users] Hello.which environment type I choose?

Dear: Hello. My name is Owen. First, I appreciate you spend time to check my email. Recently I want to use oVirt to build a project. But after reading the official document, I have some questions to ask. The project is intended to set up a physical server that is used to implement virtualization, Variable quantity of thin clients for users. But I don't know which environment types I should use to deploy. The number two question is why the system environment is different between each version of o-virt？Because centos 7 is the major version. But so many versions of o-virt is not centos 7 or centos 8.can you tell me the reason. Thank you.At last, I have a question.I ever joined the IRC, but there is no response to answer my question. Could you tell me where I can take part in the community with developers who develope o-virt.Thanks