One question at a time.
Yes, with a good fire in your basket, opening up the top vent all the way and pulling out the drawer on the bottom vent, you'll be amazed at how fast the temp screams up. We're talking a matter of a minute. You can actually watch the dial on the dome thermometer moving. One tip - take out the dome thermometer before it goes offscale high. You can affect the calibration if it ranges too far; and while easy to recalibrate, it's just better not to have to. On that steak cook above, I ran back into the house for just a moment (I'd forgotten the plate) only to come back out and see my dial reading 200F - but it wasn't 200F, but 1000F as it had over ranged that far!!!
To Robert's point, it's a matter of control and trying not to over/under cook the steak. When it's down in that roaring flame, it's really hard to stick a meat thermometer in there and check the temps. Otherwise, you're just guessing cooking solely by time. With the reverse sear, you know where you are after the initial roast. And, as long as you are careful with the sear, you're going to be pretty close on your final meat temps. I'm using this technique almost exclusively now that I'm doing sous vide, but was already a convert before that. YMMV.