I have a DSTN (dual scan screen) 1200 and a TFT (active matrix screen) 1200.
I would say in all cases you want a TFT screen display...anything else will be smeary and blocky...no matter what environment you are in.
For interior use definately use the color TFT screen.
If you need more power than a 120p1, you can get a 2300 with a 233p1. (most 2300s come wiht the TFT screen)
As far as the heat subject...there is a heat pipe from the processor that goes over to where the battery is and distributes cpu heat there...also I have noticed that the opposite side of the case at the IO ports seems to get hot.
I run it for hours and the temp never gets above that warmth you feel...in other words it doesn't get so hot that it burns...but it does get toasty near the IO ports...I would say that if you don't touch the metal by the IO ports then it does not get too warm to use.
So put a cover over the IO ports to keep it more comfortable.
BTW a big fast hard drive will make the back of the machine guite warm also.
If money is no option, then get the newest machine...around $5k.