One problem with dropping the year from our product name (it’s System Center Configuration Manager now) is that it can be tricky to search for documentation!
One page I visit almost weekly is the Supported Configurations page.
Here is the landing page for the ConfigMgr Current Branch (CB) Supported Configurations
Here is the page outlining supported client counts (how many Intune devices do we support?) and site system scale (how many MP’s do you need?)
Here is the page describing the SQL requirements (CU requirements, collation requirements, etc)
And finally, the page listing recommended hardware specs for ConfigMgr