Yes, you can configure all your jobs to start daily at 20:00 and set the maximum number of concurrent jobs to 3 (should be done in backup proxy settings). While the first 3 jobs will be executing, others will be put into a queue and will wait for the available slot on the proxy server. This will allow you execute all your jobs one by one and ensure that you do not have more than 3 jobs running at the same time.
For more details on how it works, please take a look at our User Guide (page 19). Thanks!