Which features of the game are account bound?

Knowledge, pets, node investments and contribution points are shared between your characters.

So is energy. But energy is depleted for each character on their own, if you have 200 energy on character 1 and gather something in the fields so you have for example 150 energy left, switch to character 2 it will still have its full energy at 200.

You can store your items in each of the city storages so your other characters can access and use those items too.

Your horses, donkeys and carts are also shared, but only if they are in the stable. If you summon a horse (or donkey or cart) on character 1 and switch to character 2 you can't use that same horse until you let it in the stable with character 1. Same goes with boats.

Could be that I forgot some things...