I provisioned my Oracle VDB using a template, and set the SGA to 16 GB. But I needed to boost this parameter. I changed the template, but nothing happened. I even did a VDB Refresh, but it still didn't work!
You can change the default behavior, using the CLI as described in the above link. You can use a reference to the template, and this will affect the VDB upon subsequent Refreshes.
Another important note: If you don't want to actually modify the template, you can modify the parameter using Oracle ALTER SYSTEM command. This can change the parameter in memory, in the spfile, or both (just like a Physical DB). However...these changes are ALWAYS wiped out when you run a Refresh operation, whether you use a template or not.