A code here points at one of your short links, not straight at the destination. A scan travels through the same redirect as a click, so posters, packaging and business cards land in the analytics you already read.
SVG for anything that gets scaled, or PNG at 1024 pixels for artwork that expects a bitmap.
Higher correction keeps a code readable when it is scuffed, folded or partly covered — worth it on anything physical.
The code encodes your short link, so you can repoint the link without reprinting anything.