(1) Preferable is to send email message with attachments with around 5 MB as instructed. Sending email to CPC-M <
IRCC.CPCMParentsandGrandparents-Parentsetgrands-parentsCTDM.IRCC@cic.gc.ca> used to be not easy last years. Not sure now. Try to send several times if it bounces back and unusual time like early morning 5 am. For peace of your mind, send through IRCC Webform also later.
(2) Just explain in the main letter when you send PCC, Travel History and other documents.
When you have time, explore this thread with search tool and the last sheet of the tracker. You can get a lot of information.