Until 3 months ago we were using Symantec Backup Exec as well. Backup Exec is still installed on the server along with Veeam (but with services disabled), for that occasion where we need to recover Veeam repository files prior to using the Veeam Backup to Tape jobs.
We had divided our Veeam main Backup job into 4 different Backup jobs to segment the repository files into smaller sizes so that the recovery time from Backup Exec tapes to hard drive repository was lower.
Took me a couple of weeks using Veeam Backup to Tape to optimise the Tape jobs - reading the help docs and the forums, but I'm quite happy with how it's now operating. IMO Anyone moving from Backup Exec tape to Veeam Tape will find differences which at first might seem obscure, but the Veeam Tape GUI is consistent. Just forget how you did it in Backup Exec and learn the Veeam method