hi, I`m pretty new to WM myself, but I thought I`d take a stab at answering ur qutns.
so far as I know any WM5 application should work on WM6.
WM - Windows Mobile is the operating system, the number at the end just tells you the version.
PPC - stands for
Pocket PC, which I believe is the physical hardware (eg your
TyTN II), as opposed to progs, which are software (eg. WM6) and run on the device.
hope this helps.
forgot to add that you`re unlikely to get a response on the best progs, you`ll need to search the forums.
if its any help I have Total Commander, viigo, google maps, pocket esword, kevtris, sudoku, etc.