How difficult will it be to take care of physical needs like hydration, sleep, and so on? Is it going to be overbearing?
Those features are only in Hardcore Mode, so theyre optional. If you find theyre getting to be too much of a hassle, you can always turn it off (although you wont get the Hardcore trophy if you do).
What can you tell us about the new Hardcore Mode?
Hardcore Mode can be turned on or off at any time, although if you want the Hardcore trophy, you have to turn it on when initially prompted and leave it that way all the way to the end of the game. When its on, players will have to eat, sleep, and drink water every day. In addition, ammo has weight, companions can die, Stimpaks heal over time, and damaged limbs can only be healed with a Doctors Bag.
While you can fast travel in Hardcore Mode, you cant if the time it would take to get you there would result in the player dying from dehydration/exhaustion/starvation.