Roles and permissions

Hi!

You can try to: 

1. add the "moodle/course:manageactivities" capability to the teachers role and
2. in the course, change the permissions for all the activities you don't want the teachers edit (one by one) to prohibit the teachers role the "moodle/course:manageactivities" capability:
   

On this way, you must be able to configure a role for creating activities but non editing the existing ones. Besides, you'll need to allow only the assign:addinstance capability if you want the non-editing teachers will be able to create only this kind of activities.

Hope this helps to you!