There is currently no conflict resolution in Meteor. MongoDB controls atomic operations, but the last write wins. You can try to do things a little more carefully by using upsert
operations, etc.
There is currently no native OT support for Meteor, but it is on the roadmap and in the meantime people like me have made packages that allow OT packages like sharejs to be integrated into Meteor apps: https://github.com/mizzao/meteor-sharejs.