The current behaviour is all email and calendar events cause a notification, or none of them do.

Desired separation between a calendar event notification and email arrival notification.

Particular case example: I do not want to be notified of the arrival of every email. I do want to be alerted about calendar events. At present, I must be notified of all emails or I will not be reminded about calendar events.

This problem would be solved with
https://protonmail.uservoice.com/forums/284483-proton-mail-calendar/suggestions/48198224-separate-mail-and-calendar-into-different-apps