Sid's for service accounts in alwayson
If they are Windows domain accounts/groups, you shouldn't have to worry about it as they should be identical on both nodes.

The orphaned user issue and SID syncing across both nodes is only applicable to SQL authorization logins.  With SQL authentication, you will have to sync the SIDs as, after a failover, the SIDs wont line up between the server level SID and db level SID.