You can submit additional docs by web form, I would say not submiting additional documents (that are necessary to the application) may delay your application because they will ask for those documents later when they review your eligibity and then give you a week to upload it and even if you upload them on day 1, they get like a buffer time to wait for a week.
Like Iambeingpatient had to wait for 14-15 days to get approved after they asked for additional docs (transcript). Am I right Iambeingpatient?
I did not know that the Transcript was necessary so I did not upload it with my application, but 2-3 weekes later when I learned that it is important then I uploaded it via web form and after 3-4 days I got a ghost update in my online login gc key, someone probably linked my transcript to my application.