Show Busy one way, full detail the other

Yes, you can. Set it per destination calendar under Calendar exceptions, in your sync's Appearance settings. This needs a Pro plan.

The usual case: you mirror Work and Personal, and you want your work calendar to see nothing but "Busy" while your personal calendar shows the real titles. One sync, two different treatments.

How to set it up

1. Open the sync and go to Appearance.
2. Set the shared default first. That's what every copy gets unless you override it. For the example above, set Use original title as the default.
3. Open Calendar exceptions and pick your work calendar.
4. On that calendar's exception, choose Title says "Busy".

Now anything landing in Work reads "Busy", and anything landing in Personal keeps its real title.

The thing to get straight: an exception describes the calendar events arrive in, not the calendar they came from. You're answering "what should copies look like when they land here", not "what should this calendar send out". People set it backwards the first time and then see the mask on the wrong side.

What you can vary per calendar

Title, colour, privacy, description, attendees, reminders, free/busy, location, and whether the SYNCDATE line appears at the bottom of the copy.

What you can't

Filters are shared across the whole sync. There's one setting for each of these, and it applies everywhere:

• which events sync at all (skip all-day, skip by title, skip by day or time of day)
• the accepted/tentative filter
• how far ahead the sync reaches

So you can't have Work receive only accepted meetings while Personal receives everything. If you need that, build two separate one-way syncs instead of one mirror, and give each its own filters.

Known limitations

• Pro only. On Free and Plus there's one appearance setting for the whole sync. If you're on Plus and you want asymmetry, two one-way syncs pointed at each other is the workaround, and it costs you a second sync against your plan's sync count.
• Existing copies don't change until the sync runs again. Adding an exception re-renders copies on the next run, not the moment you save.
• If you downgrade from Pro, exceptions stop applying and every copy falls back to the shared default. The exception isn't deleted, so it comes back if you upgrade again.