Why dynamic beats static
A static QR code has the destination baked into the pattern itself. Once it is printed on a thousand flyers, the URL it points to is fixed forever, and a redesign that moves that page turns every one of those flyers into a dead end.
A dynamic code encodes a short link instead, and the short link is a record you can edit. The pattern on the flyer never changes; where it sends people does. That is the difference between a campaign you can correct and one you have to reprint.
Tagging links so the numbers mean something
Analytics can only report on what the link told it. A URL shared without campaign parameters arrives as direct or referral traffic, indistinguishable from everything else that came in that way, which is how a campaign ends up looking like it did nothing.
Building the parameters before you shorten the URL keeps the tags intact through the redirect, so the link you hand out stays short and the destination still knows where the visit came from.