Difference between activities such as walk and hike?

Hi, I’ve only had my fenix 6X Pro for a couple of days and trying to get my head around things such as the activity modes.

Are there any fundamental differences in the way the device operates between say using the modes Walk or Hike?
Does the device function differently, or do they just give you a different default set of screens which could be changed to be the same anyway?

If I create a course in Garmin Connect and call it a Hike, is it only available under Hike in the watch etc?