You can select any instance type which has 16 cores with hyperthreading and with a minimum 2.0 GHz or Higher CPU.
We recommended having Centos8 (64-bit) but we also support the Ubuntu, Redhat server as well.
And Yes, We need a significant RAM to perform the application. For more information, please check out our Hardware Requirement Document.
For installation, It requires to share the HostName or IP and UserName with Password or Key to access the Instance, It can be anything Key or Password.
If you still have a question regarding the instance or server specifications, you can always contact RChilli Support via creating a ticket at RChilli HelpDesk or simply by sending an email at firstname.lastname@example.org.