First, RWD drift is perfectly possible, but it requires alot more work to get it to work right. The big problem is that RC's dont have the right... well much anything to do it naturally, so it requires some modification, including a massive boost in front end weight, and extreme turning angle. Some dude around here made one work VERY well, should look it up.

As far as the off roader drifting, not unbelievable. Infact very possible you just gata set it up right. Golden rule is, with enough enough time and effort, any 4wd rc can drift just fine.