You can travel from the mainland to other areas. However, the journey is really really hard (prime roots are very hostile areas). Some have already succeeded, with great losses, patience and some chance.
There's not a real difference between the races apart from their look and their environment. Each mainland is different, some are a bit easier to survive in (Tryker for example, until aquatic mobs are implemented, but we, Tryker, are joyfull and harmfull people
), some more difficult, but they are quite well balanced (but there're always people complaining they can't travel everywhere, explore all the maps and kill all the mobs after having spent two days in Atys
).
Paera - and her poor english