The simple answer is no. As a Vietnamese person, as opposed to EB-5, you would not be subject to backlog issues. You may wish to consider QIIP (Quebec) as an alternative to EB-5 because it is the only program with passive investment leading to PR in Canada.
Is there a visa backlog for investors coming from certain countries for any Canadian provincial immigrant nominee programs?
I heard that there has been a long wait for investors from China in the past. I am from Vietnam. Will I face a backlog? Vietnamese applicants to the U.S. EB-5 program are dealing with a backlog now, and that program is getting slower and slower, so I am weighing other options.
There is no equivalent of retrogression in the Canadian immigration system. Some programs put a quota on China (QIIP), but usually there is no such thing. Vietnam is not affected by any limit for any Canadian program. The waiting time at the Canadian consulate in Singapore, which serves Vietnam for PR, depends on which category you will apply.