Best practice to add addtional database post deploy on VM-ODA x7 HA

Since last year, our production databases have resided on a VM-ODA X7 HA system.  Now we would like to move 2 non-prod databases (both 1TB, 42gb combined SGA)

1. What is the best way to keep the prod/non-prod resources separate?  i.e. oracle home, file system, CPU, etc.
2. Would it be best to create a repo or separate VM to accomplish this?
3. Is it acceptable practice to comingle Prod and non-prod together on a single ODA architecture?  It seems to me that is how Oracle advertises it....does anyone out there currently do this?  If so, h
4. The databases we are wanting to move are masked databases (duplicate of prod), therefore approximately once per month we mask the databases using EM ADM - which is a very CPU intensive process.