I just got my tmv7a, so I can't answer your questions as well as others
can, but if you're so enclined to spend the $35 for the computer cable,
that is the easiest way to go.  If not, you can get sighted help to turn
on mike control in the menus and I'm told, but haven't actually tried it
yet, you can enter the pl number from the mike key pad.  I wouldn't pass
this radio by on that account.  I think it is mostly if you want to spend
the difference, if you want dual band, ccrossband repeat and so forth.

I'm amazed at the receiver speks these days.  I haven't put mine on the
ifr yet, but the book says .16 microvolt for 12 db sinad.  open squelch at
less  than .1.   I'll hook mine up to my service monitor soon and report.
73s
Butch Bussen
wa0vjr