As far as I know there's a setting on which we could set the default homescreen back to the old android style. But yeah blinkfeed will be the default on factory setting. Same goes for the 3x5 app drawer. You can set it to 4x5 also. Not sure about the horizontal scroll though and yeah horizontal one is alot more better if you ask me.
Regarding root the moment any even average developer who knows how to extract and repack ramdisks get's a hold of the phone then root should be available. I for one can create a rooted phone in just a few hours. Just
Unlock the phone, dump the kernel, extract ramdisk, insert root there, repack ramdisk, reflash kernel = root. But making a custom recovery to root the device is another thing..
And yeah for me the first thing I'm gonna do when I get the phone is the most grandest of all!!!!!!!!!
Press the power button!