I don't know if the Platinum broiler differs from the RNB, but I'll answer your questions abut my 36RNB.
The broiler cycles on and off, which is frustrating unless you leave the door partially open, which I do.
Hint, pull the drip tray out an inch or two, to help deflect heat from the knobs.

You cannot change the temperature, which I also do not like, it's full tilt only, and very HOT! The top grate is way too close for most anything, but trial and error will tell you how far down for what foods, and results you want.

I think the broiler is rediculously small for such a large oven! ...It is 8"x11" in an oven that is 20" x 29", makes no sense.

Fortunately for me anyway, I don't broil much because I can grill outdoors year round. Although I do struggle with my famous garlic bread which would come out perfect in my old Thermador wall oven with the broiler turned down to 400....

Hope this is of some help, Chris