Play another char doesn't worth anything, simple because the incarnation shares with the main a lot of stuff like: bag/bank slot, some Boutique items (like Wizard's trinkets"), *runes* (because the patron is the same) and mounts.
In addition the main can give to the inc one of the 2 sharable skills and vice versa (but the main can take the skill only when the inc it's cap level, with this patch).
it's true incarnation have a debuff that decrease your damage of 33% and make you loose a 10% of the exp you have for that level if you die, but it's nothing so evil like it seems <.<
So, when you reincarnate you can generate a new incarnation of any available class/race combination. But can you also change the sex?
it's another pg, like when you create it from the initial panel. So you can change sex as well.
can you set it to the class of any reicarnation that you have meaxed
Nope. The only way to change class to a char (main or inc doesn't matter) is buying the core morpher on the Auctions (paying with gold to take it, and with CC after to buy the right item from the shop).
And the only way to change sex/look to a char is to go to the NPC on the faction (you can see him on the map, there is a little pink mask. For us it on the 2nd floor of Imperial Square
To make the changes you have to buy the currency from the shop <.<)