I sold mine many years ago, but when I did have it, I used the 9 pin RS-232 connection on the computer for programming.
I don't know if they even make a USB cable for it, or if any of the newer ones will work. I also never tried a USB to RS232 adapter with it.
High power is about 35 watts.
Low 2 power is about 10 watts.
Low 1 power is about 4.5 watts.
At least that is what I recall mine being. It's very likely that yours will vary. I seem to recall there was a way to adjust the power levels, but it's been so long since I've touched one of those I'm probably remembering something different.
I ran mine on 70 centimeter amateur band and GMRS (back when I still had a GMRS license). I know I had the Low 1 power set for 5 watts or below.
Decent radio. At the time when I purchased it (around 1997 or so) it was one of the less expensive remote head capable radios.
I did have the 160 channel memory chip in it, so had plenty of space for the amateur, GMRS and RX only stuff.
Only issue I ever had with the radio was the Push To Talk switch on the hand mic gave out after a while. I ended up replacing a lot of those buttons over the years (I had several Icom radios, plus a few at work). Somewhere, squirrel'd away somewhere in a box, I've got more of the little buttons .