Taking EBS snapshot for multiple mongo node EBS volumes in mongoDB cluster

I have journal and data both on the same volume for a mongoDB shard, so the consistency problem of taking snapshots only after locking using fsyncLock is not needed. An EBS snapshot would be consistent point in time for a single shard.

I would like to know what is the preferred way of taking backups in mongodb cluster. I have explored two options:

1. Approximate point in time consistent backup by taking the EBS snapshots around the same time. Advantage being, no write lock needs to be taken.
2. Stop writes on the system, then take snapshots. This would give point in time consistent backup.

Now, I'd like to know how is it actually done in production. I've read about replica set's secondary node being used, but not clear how it gives point in time consistent backup. Unless all the secondary nodes have a consistent point in time data, the EBS snapshot cannot be point in time. For example, what if for a secondary for NodeA, data is synced with primary, but some data for secondary for NodeB is not. Am I missing something here?

Also, can if ever happen that approach 1 leads to inconsistent MongoDB cluster (when restored), such that is crashes or stuff?