A couple of questions for AD8336

Dir Sir/Madam,

I have a couple of questions for AD8336 as following.

1)

What is the input-impedance of VGAI pin?

I can see the 1.28kohms on your datasheet page-20.

Does this means the impedamce,correct?

2)

Why is LPF(low pass filter) put at AN-934 page-4?

(closing output pin, 100ohm and 4.7nF)

I think that this means 36kHz cut off frequency.

eg) If I need the 20kHz cut off frequency, can I put the 20kHz LPF there?

3)

If I dont use the internal preamp on AD8336, how can I deal the opened 3 pins INPP, INPN, and PRAO?

In general, connect INPP to GND, and short INPN to PRAO, correct? It is similar as voltage follower circuit.

Thanks, KAOS