Multiple backup plans targeting the same destination storage , thanks for your question.
You can run several plans backing up to the same storage but only if the backup sets are different.
Technically, it would work even if you pick the same folder to backup in two plans. Let’s say for over plan you have 30 days retention and for the second plan you have 7 days retention. I’d run daily, the second plan will keep deleting backups older than 7 days and the first plan will never reach 30 days of recovery points.
Also, it’s a good practice to split a hard drive to smaller partitions, back up system partition with image based backup, data partitions with file-level backup or SQL our exchange backup if applicable.
Thanks