“what happens if I run the app from the current location (running it from the DMG) without dragging it to the applications folder?”
In general, it works just fine (if it doesn’t, it’s a broken app). It also works fine if you want to drag it to another drive, put it in a folder called TarquinFinTinLinBinWhinBusStopFtangFtangOleBiscuitBarrel, or launch it from a network drive.
Now, what happens if you copy the average Windows application ANYWHERE other than C:\Program Files after it’s installed? Answer: it breaks. Horribly. What happens if the C drive gets full and you want to move some of your large apps to the D drive? Answer: you get to reinstall them all again. Good luck finding all those CDs and serial numbers!
Deleting the app, as others have noted, consists of dragging the application to the trash. No “uninstall” crapola. No reboots to (hopefully) clean up the fifty little files that the application has scribbled in random places on your drive, either.
In fact, you don’t usually have to reboot for anything except upgrades that alter the OS itself.
Stuffit hasn’t been needed to open zip files for a LONG time, by the way. It’s essentially useless on a modern Mac, unless you’re downloading and running old, old, old software.
I’m not sure why Batchelder has a hard time “finding the Applications folder”, by the way. It’s right there in the Finder window when you open it up. You just click on it. Need I mention that doing that does NOT produce a dire warning about how you’re not worthy to even see the contents of that folder, lest you destroy your computer?