Can a sub-account use the master account’s custom templates?
Yes. On your master account, when you set up a customized template at the bottom of the page, mark the checkbox near "Sub-Accounts" to make the template applicable for sub-accounts.
You can also quick-add/remove the application for sub-accounts from the tables of existing custom templates.Note that in addition to the templates you make applicable for sub-accounts, sub-accounts users can also create their own customized templates.