Yes, same seed but you need to keep the scale the same as well otherwise it goes out of sync. You can of course totally mess around with detail, spike limit etc. Even warp slightly, probably. Other slight variations such as clumping might be OK.
I've been investigating a kind of altitude blended terrain. You can't get altitude until after terrain is calculated but you do have the terrains value output to use as blend. My tests are still half baked though. I don't like posting things like this because half baked graphs end up causing confusion. Best to sort it out first.