In order to run self-hosted parallel jobs, you need to purchase parallel jobs and register several self-hosted agents.
For parallel jobs, you can register any number of self-hosted agents in your organization. If you want to run 3 jobs in parallel, then you must register at least 3 self-hosted agents in one agent pool. DevOps charges based on the number of jobs you want to run at a time, not the number of agents registered. There are no time limits on self-hosted jobs. For private projects, you can have one job and one additional job for each active Visual Studio Enterprise subscriber who is a member of your organization.
About how to purchase parallel jobs, please refer to Buy parallel jobs.
For how to control the use of parallel jobs, please refer to the following:
- For classic pipeline, you can specify when to run the job through dependencies and Run this job in Additional options in the agent job. Then the pipeline will run in sequence according to your settings.

- For YAML pipeline, you can specify the conditions under which the job should run with "dependsOn" and "condition".
For example:

For more info about conditions, please refer to Specify conditions
If you don't specify a specific order, the jobs will run in parallel based on the parallel jobs you purchased.