Well I started splitting at age 28 i think. My plan was to stop competing at age 30 so i wasn't really worried about imbalances over that short of time span and considering the squatting I was doing ect. Now I'm sneaking up on 32 and I still compete & split & there are noticeable imbalances that I'll want to take care of some day. My leg I put forward is much stronger and I've noticed that one side of my lower back has developed more than the other.
I use the same leg forward everytime becuase i compete. The athletes i train that are using split snatches to train for sport I have them alternate at least some of the time (they really don't do enough volume to develop significant imbalances) other ways to prevent the imbalance include overhead split squats and front split squats done for equal sets/reps on each leg.
As far as the split clean goes it felt very natural for me from the begining. I basically do a power split clean unless i need to get low to recieve the bar. getting low to get a heavy clean feels natural and is no problen even though I never practice it. Trying to get low in a split clean feels incredibly akward and is difficult for me to do with lighter wts.
hope this helps, Josh