ESC to use?

[roadranger]

OK, more questions;
Seems like the Castle ESC's need to be programmed with a laptop?
Most others are field programmable?

Can someone explain how 'drag' and 'regular' braking work?
What's the difference between the 2?

And what about protection against pulling into reverse while trying to brake on a downslope?
Is there a feature for this?

The Tekin sounds good, but being so small, can it handle the size/weight of these trucks?
My trailers with loads on them are pretty heavy - in the 20 to 25 pound range on ball bearing axles.
What kind of heat buildup on stiff grades?