Regarding two backups scheduled at the same time, the “Maximum Parallel Snapshots” policy setting determines the maximum number of snapshots that can upload at the same time. As long as you have that set to 2 or higher, then your two backups can run at the same time. And the inverse is true, too: if you only want one to run at a time, then set it to 1. You can find more detail in this post
As for the time of day, I had a similar problem. For me (and I would guess for you as well), what was happening was that I had a global policy that defined a time for my backups to run, and that was a good time for most backups, but there was one backup I wanted to run at a different time. So I set a different time for it, but that only added an additional time that it would run (like what you’re seeing). To fix that, I had to set that one backup’s policy not to inherit from parent. To do that, I used the following command:
kopia policy set /path/for/my/policy --snapshot-time "01:00" --inherit false
The --inherit false arg sets that time in place of the time set on the parent (global) policy, rather than in addition to it.