So let's see if I got it right. The main differences between Quick Resume and Activity cards/Switcher are:
Quick Resume
-Resumes exactly where you left the game in the last game session (correct)
-Not all games support it (wrong, its a system level feature..some games will fail if internet connection is required)
-Works with a few games you recently played, not all the ones you have installed in the console (its a cache so yes it only the most recent games)
-Requires dozens of SSD GBs because basically dumps the game RAM in the SSD (who knows what it requires exactly, but at the end of the day you still have more available space than the xbox one x 1tb HDD)
Activity cards/Switcher
-Resumes to your last checkpoint savedata in the last game session (is there a universal last checkpoint/autosave card?)
-In all PS5 games also acts as quick, direct access to specific tasks, stages or game modes skipping menus/logos (varies per game) (depends on what the developer chooses to give you as cards)
-All games support it (savedata checkpoint, the quick access to specific game parts is exclusive to PS5 native games) (only ps5 games support it now, and its what the developers choose to do with it)
-Works in all the games you have installed in the console, not with the few you recently played (ps5 games* because its not a cache and again, its up to the developer to give you those options)
-Doesn't require extra SSD space because it basically uses the normal savedata (you have 667gb of useable space onboard regardless)
Please can someone correct me if I'm wrong in something?