When you limit the number of concurrent backup processes to 1, only 1 process will run at any specified time, forcing other processes that might be configured to run at similar times, to wait until its completion. If you have a second, third, fourth backup configuration, e.g. in individual domain settings, these will wait on one another and no longer run at their specified time. This traffic jam can lead to a situation where the queue becomes so long that on the next day all the backups scheduled on the previous day are still not finished, so that the next day starts with a delay and following backups are delayed even further. This will lead to a continuously growing queue of backups. You will have not control over the actual time of backup execution.
Normally, on a system where you have a central (administrator) backup and customers on the machine who do their own backups, a value of "2" already resolves this issue, because most systems don't have so many backup jobs that a value of 2 can lead to a similar situation. I am just say that "1" ist likely to lead into issues much more than a higher value like "2".
Normally, on a system where you have a central (administrator) backup and customers on the machine who do their own backups, a value of "2" already resolves this issue, because most systems don't have so many backup jobs that a value of 2 can lead to a similar situation. I am just say that "1" ist likely to lead into issues much more than a higher value like "2".