I like new templates that came with v3 for SNMP. But they don't have any alerting. If I add those myself or modify templates, will future updates overwrite my changes to them?
In Server configuration parameters there's a parameter called ImportConfigurationOnStartup. By default it's set to "Only missing elements". In this mode, server imports default templates only if such template is not present in the system. Import happens on each server startup. If template is present, server does not overwrite it.
This means that you can modify the template and it will not get overwritten. If you delete it, it will get recreated on next server startup.
What are they matched on?
Name? id? guid ?
Templates are matched on guid.