GMU is the specific unit that applies to the game you are hunting within. GMU's can have different hunting seasons, legal species whereas other GMU's may be entirely closed for example.
Deer/Elk Areas are specified portions of one or more GMU's, or parts thereof, that have different regulations then the entire GMU. Sometimes they can be in addition to regulations.
All of the public lands you mentioned, you can pretty much park along side any open road you are legal to drive on unless it's posted otherwise. They all have different restrictions on how far off the road you can legally drive to just to park. You keep within a couple truck lengths of the road and you won't get hassled by enforcement.
Remember your Discover Pass if you are on DNR or WDFW lands. Enforcement likes to generate revenue thru writing tickets for no DP....