On most newer devices (Newer than GB) the internal memory is much larger to store apps on. On your Samsung phone, the SD card mounted to the /sdcard/ (or /mnt/sdcard/) directory. On your tablet, the internal memory is mounted there. It actually makes much more sense to install apps to the internal memory (do you install Firefox, or any games on a USB hard drive on your PC?)
IMO, the internal storage (even at 16 GB) is more than enough for apps, unless you are a hardcore gamer and install a bunch of 2-4 GB games.
I keep movies on the external, music on the (google music) cloud and docs/apps on the internal.
As far as using a camera to save to the SD card, there are some camera apps (cannot remember the name off the top of my head) that allow you to save to the SD card and not the internal memory.