I think the way it is for larger mammals is the same - it got crowded, so pressure evolved in one direction: away from the crowd and towards more food, better hunting. Sure, there were exceptions - some may have wandered towards less food, worse conditions. Just that on the average, populations tend to spread out to "fill the room".
The movie "Ao, the last Neanderthal" depicts some of this. Cool prehistoric docu-drama-comedy.
I’m sure you are right. There was probably a lot of unintentional “experimentation” going on. Those that headed in the wrong direction, say toward the hot, sterile desert, perished. You could say that was early Darwinism at work. Those that moved in the right direction toward a more hospitable climate and more food thrived.
That still doesn’t explain why people would leave fertile areas and head north toward Siberia to cross the land bridge. That’s a real head scratcher. Maybe they developed an affinity for seal blubber.