1. Standup - 10-15m (face time) Monday / Wednesday 2. Async (Slack channel text) Tuesday / Thursday 3. Planning - 30m-1h (face time) Friday 4. A rotating "lead" or "on-call" or "captain" for the week who organizes these things and interfaces with other team's standups
This, in combination with your work queue (ticketing / kanban board / issues / etc) is the most streamlined approach I've seen that works. You can certainly add more ceremonies, but I find the constant retrospectives of other systems too negative and depressing, and too much of a distraction.
"Rally" is not a new take on standups, it's just scrum with a friendly coat of paint on top IMO. One thing that rubs me the wrong way about "Rally" in particular is the forced-socialization ideas. When I'm at work, I'm at work. Sometimes, there's people at work that I'm not friends with, but I am going to work with them because I'm a professional and I get the job done. Don't force people to be friendly. It's kind of toxic, and forces people to hide their opinions and play politics more than is necessary.