Ola Hallengren Maintenance script - Full database backup delays
It will depend on the resources available on the server.


  Does it take same amount of time even when the backups are made to run
  at the same time at 2AM(by different jobs) due to IO overhead?


You can set up parallel jobs and test.  You will need to watch, how many of full backups can run in parallel before other processes (if any) are effected (cpu, io, network bandwidth etc).

Recently there was another question where Brent Ozar explained the phases of backup and how you can test.

I will not repeat his words but you can check details here.

There are built in switches in SQL Server that you can use to speed up backup.
See this blog post.

I did not understand this question?  Did you mean if full backup run in serialized way?  Depends how you job is set up. You can make them parallel as @Ghauan explained in comment, you can make multiple jobs to run in parallel.


  Is this the normal way the FULL backups are made (with delays)?