That manifold will allow you to direct gas to 3 separate kegs. The pressure will set by the regulator which is most likely going to be placed between that manifold and the CO2 tank, soo.... No, your pressure would be the same on all 3 lines. I also HIGHLY doubt that manifold is good for the full cylinder pressure without having a regulator between the manifold and cylinder.
All, for what its worth, I maintain my beer in my keezer set to 28 degrees F. It modulates between 28 and 32 degrees F, and in the past I have noticed slight icing after i thought I had floated the keg and opened it up to find out I have a nice layer of ice remaining in the bottom, but never noticed any issues with freezing solid. Not everyone prefers to keep their beer that cold, but just my $0.02 that a temperature like that has not ever caused any adverse affects. On a side note, the icing issue only happened on one keg and i believe i had my keezer colder than it currently sits. My last keg (floated 2 days ago) had zero icing.