The Evernote limits are identified here https://help.evernote.com/hc/en-us/articles/209005247-Evernote-system-limits
fwiw My templates are stored as a collection of notes identified by tag: !Template
I've automated processing with scripting (Mac). Duplicate Note also works.
Pretty sure I saw another thread somewhere here confirming that the current limit is 20, but implying that there will be more options in future. It's a new feature, so I'd guess the teams don't want anyone basing a whole operation on templates just in case there's an overwhelming need to drop / suspend the service in the short term. Once any bugs are worked out - or they've added all the necessary bells and whistles - there will presumably be a more complete roll-out.
In the meantime as