1st being that my whole layout will be dcc would it be a good idea to go ahead and wire the yard and the round house to the main.
2nd would it be possible to add a second level on this layout with what i have as track placement. also being able to get a train from level one to two and explain if you could. here's the layout.
3rd what should the track spacing be for n scale around curves mine are 1 & 3/4"'s center to center. i hope i got enough space for the kato superliners and atlas autoracks not to clip anything going around curves of 19 1/2", 21 1/4", and 23" radius's.
thanks in advance
To answer your wiring question, I would put separate toggle switches on each yard track so they can be turned off. You may want to park a sound-equipped locomotive on one of those tracks someday and turn the track off so the sound doesn't continually draw power from your DCC system.
For your other questions, my opinion is that you have too much track crammed into too small a space and there is no way you have room for a ramp up to a second level.