I would suggest taking a look at your scan queue. Depending on how many assets you scan it might be that at mid day scans can take a long time because the queue is so long.
IP and computer threads kinda depend on the server Lansweeper is running on an what it can handle. It's something you can experiment with while keeping an eye on resource usage.
Theoretically, domain pc's should be discovered within 15 minutes after logon on default settings.